Bill Walsh said he needed two years to know Joe Montana would be the San Francisco 49ers' franchise quarterback. Walsh's coaching understudy, Mike Holmgren, generally thought the third year was when a starting quarterback should hit stride.

Waiting around for a prospect to develop into a franchise quarterback creates risks for decision-makers. Big bets made on Kevin Kolb, Christian Ponder, Blaine Gabbert, Mark Sanchez and others come to mind. Another wave of young starters -- Nick Foles, Cam Newton, Jake Locker, Ryan Tannehill, Andy Dalton, Matthew Stafford, Sam Bradford and Geno Smith among them -- carry the hopes of their franchises into the 2014 season.

Teams need answers sooner than later. What if how a quarterback plays right away tells an organization what it needs to know? Evidence collected over the past eight seasons supports that thinking almost without exception, providing a clear lens for viewing the game's most important position.

"The QBs who do well ultimately, do well as rookies or in their first season of starting -- they show you," ESPN analyst and six-time NFL executive of the year Bill Polian said. "If they are not above a certain threshold after their first 16 games, the odds are pretty good that they will not be a franchise quarterback. The odds are even stronger that they will wash out completely."

We have found strong trends among the 41 quarterbacks making their first 16 starts over the past eight seasons. The QBs with the worst performance metrics over those initial 16 starts flamed out. The fast starters reached the playoffs in every case, playing in three of the past five Super Bowls. Their futures appear bright. The QBs in the middle look as though they'll remain there in the majority of cases.

Every situation is different, of course, and many factors dictate whether a quarterback ultimately succeeds, but there have not yet been many exceptions to this general rule.

What do the numbers tell us about the league's newer starters (including RG III, Foles and Geno Smith), and the QBs who enter the 2014 season at a crossroads (including Bradford, Newton, Stafford and Dalton)? Let's take a look.

The seven fastest starters are on their way

A four-year body of work allows for definitive evaluation in most cases, and Total QBR agrees. The metric, explained here and vetted most recently by Chase Stuart of Football Perspective, identifies the best quarterbacks over time. For example, a look at quarterbacks with at least 60 starts since 2006 showed Peyton Manning, Aaron Rodgers, Tom Brady, Drew Brees and Matt Ryan as the only ones with QBR scores above 65.0, which ESPN has identified as a general cutoff for Pro Bowl-caliber play. Sixty starts was the cutoff because that is roughly how many we might expect a quarterback to make over the four-year period Polian thought was sufficient for a full analysis.

QBR Leaders: First 16 starts*

With guidelines for top-notch play established, I pulled together a list showing the 41 quarterbacks who made their first 16 starts over the past eight seasons. We chose 2006 as the starting point because that is how far back the Total QBR data reaches, and eight seasons seemed like a manageable time frame.

The first chart lists the seven players sitting atop that 41-player list. These are the quarterbacks with the highest QBR scores over their first 16 games. Every one of those players appears headed down a generally successful path, with a couple of concerns: RG III stands out because his performance fell off last season following a knee injury, and Colin Kaepernick has played less than the others.

Generally speaking, an especially strong first 16 games in the absence of an injury such as the one Griffin suffered seems to foreshadow continued production whether or not the player went to a strong team. Philip Rivers was the next player on the list with a 60.1 QBR score for his first 16 games. From there, the names become a blur of mediocrity, crossed fingers and worse.

Ominous outlook at the bottom

The second chart shows which of the 41 players had the 15 lowest QBR scores for their first 16 career starts. The bottom nine -- Brady Quinn through Gabbert, with five first-round choices in that range -- have pretty much run their course as viable starters. Some of them, such as Sanchez and Tarvaris Jackson, played for teams with outstanding defenses. That helps explain why those two had better won-lost records than the other players with especially poor performance metrics.

QBR laggers: First 16 starts*

The information in this second chart supports the idea that players who struggle to produce early do not succeed in the long run, either. The implications for Stafford, Bradford and Smith are of particular interest. Stafford and Bradford joined terrible teams as rookies. Stafford has played better more recently, and Bradford has shown some positive signs without sustaining success. But neither has established himself as a consistent performer.

Smith, meanwhile, has played just one season. Conventional wisdom says it's far too early to draw conclusions on a player who was rushed into the New York Jets' lineup without sufficient weaponry to support him. That could be true. But we also know that a 35.9 QBR score through 16 starts puts Smith in a potentially precarious position one slot above the nine flameouts. As Polian said, the good ones tend to produce at a higher level right away, even when they join teams that had losing records before their arrival.

A quick look at the middle

The next chart shows quarterbacks falling between the two extremes through their initial 16 starts. Nine of the 19 are projected starters heading into the 2014 season, but of those nine, only Rivers has established himself as a consistent upper-tier quarterback. As noted, he was quite productive through his first 16 starts.

QBR middlers: First 16 starts*

For reference, consider that QBR scores correlate closely with winning percentages, so that teams averaging a QBR score around 50 will win about half their games over time. Eight of 39 qualifying quarterbacks finished 2013 with scores of 65 or higher, while 10 were beneath 40. Some of the players we're most interested in analyzing fell between those extremes through their first 16 starts and have yet to take a big step forward, so precedent isn't particularly encouraging.

A head coach and team executive consulted for this piece liked the research without buying in completely. The coach thought running the ball successfully was the No. 1 variable for most quarterbacks in general. He thought a team's commitment to the ground game was largely responsible for separating the "successful" and "unsuccessful" players listed in the charts. The executive said there were too many variables for a single performance metric to tell the full story.

"One of the arguments against metrics is, this is a team game and highly complex and not easily measurable," Polian said. "On the other hand, I think you could hypothesize that because the quarterback position is so important, there needs to be an objective way of measuring how that guy is performing and growing. It is not perfect. There are no absolutes. But it does give you at least some pretty serious food for thought in terms of how you construct your team and what your quarterback might become. The hypothesis that they will show you something early is overwhelmingly true."

So what does all of this mean for the league's young quarterbacks? After removing RG III, Wilson, Kaepernick and Luck for having cleared a Pro Bowl-caliber performance threshold through their first 16 games (that's not to say they're sure-fire successes going forward, but nothing in their early-career performance indicates any cause for concern), we looked at the remaining eight starting quarterbacks younger than 27 years old based on the QBR scores they posted through their first 16 starts, grouping them into three separate categories.

QBs at a crossroads

Polian placed Dalton, Stafford, Bradford and Newton into a general "crossroads" category. Each has between 48 and 61 starts, has started right away and hasn't won a playoff game. Dalton, Bradford and Newton will be in line for new contracts in the not-too-distant future.

QBR scores, then and now

Cam Newton (56.2 QBR in first 16 starts): Newton belongs in a separate subcategory, Polian thought. "Newton is a special guy," Polian said. "He is a single-wing tailback, like a Tim Tebow with passing ability, which makes him totally different. The question is how long he can absorb this much punishment. There is no one like him. He almost plays a different position."

The metrics say Newton has already been pretty good, and he hasn't yet missed a game because of injury (although he did undergo ankle surgery this offseason).

"I think he has been sold a tough gig, too," ESPN Insider scout Matt Williamson said. "When he was the Heisman winner at Auburn and everyone said [he was] a project, a one-year starter, that was true. He comes into the league and wisely they run the read-option when Tebow was the only other guy doing it. Then they decided to make him into a pocket passer and he plateaued a little in 'SportsCenter' highlights, but the whole project has been a success."

In putting together the list of 41 quarterbacks making their first 16 starts, I wanted to know which ones had the strongest defenses and whether that affected their production. Expected points was the metric of choice for reasons explained here. There was naturally strong correlation between defensive strength and won-lost records, but there was none between defenses and QBR scores.

The worst defensive contributions, by far, belonged to the Panthers in the 16 initial starts Newton made. Bradford actually got better defensive support than Wilson through 16 starts, one reason the Rams went 7-9 during his rookie season despite a 38.2 QBR score from Bradford.

Matthew Stafford (40.3): Of the four crossroads QBs, Stafford is the only one to make a significant statistical leap since his first 16 regular-season starts. His QBR score was at 40.3 in his first 16 starts and has been at a much more respectable 57.3 since then. The others remain pretty much what they have been, at least from a QBR standpoint.

"The jury is out," Polian said of Stafford. "He has been playing in Detroit with the best front four in football and a decent enough running game and a great wide receiver, and he still makes mistakes. You would have to say the arrow has been up with him. The question is, is he going to take the next step? The Lions paid him, but they hired Jim Caldwell because [Stafford] needed more consistency."

"I'd take him over Cam, Tannehill, Locker and Bradford, for sure," Williamson added, "but he needs to be coached. His mechanics are dreadful."

Andy Dalton (49.8): Dalton has played well enough to get a good team to the playoffs, but not necessarily well enough for the Bengals to feel great about paying him $18 million a year or more, which can be the going rate for keeping an established starter. Dalton is entering the final year of his rookie deal.

"I think he is what he is, and he will never change," Williamson said. "He will be too good to cut and not good enough to win with. He wins three or four [games] a year for his team and loses one or two, but he is so much less gifted than all the others guys we are talking about here. Maybe if he was playing indoors, he could get away with it more."

"Dalton is a hard, hard, hard guy to read," one NFL general manager said. "He plays really well and really badly. It is surprising. He is not dumb. And it's not like Jay Cutler, who forces it because he has the arm and the ego. Dalton is not that way at all. Something is missing."

The Bengals think renewed commitment to the running game can take pressure off Dalton and help him become more consistent. I've advocated in the past for the Bengals to draft a quarterback for insurance and possibly more, and with his rookie deal set to expire in a year, the stakes are only getting higher.

Sam Bradford (38.2): "I'm not done with Bradford, but the Rams were better without him last season," Williamson said. "They changed their philosophy and maybe should have done that from the beginning, but the personnel wasn't that much different. How many great games has he had? There are lots of reasons why and I'd still give him this year, but that is it. For Newton, by comparison, I'm all in with him."

We should expect the Rams to take a similar run-first approach to the Bengals this season, after experimenting with a pass-oriented offense early last season, before Bradford suffered a torn ACL. Regardless, Polian thought Bradford was easy to read.

"You have a tendency to say he is in limbo, but he has not done anything and he has been hurt, as he was in college," Polian said. "You see flashes of good things from him. The only question is, can he stay healthy and can he do it on a consistent basis? You don't have enough to go on there."

Varying levels of optimism

Nick Foles (57.8): Foles had a 1-5 record with a 44.9 QBR score as a starter under Andy Reid in 2012, but he was significantly better under Chip Kelly last season. "Let's judge him in Kelly's system, where he will be judged going forward," Polian said. "The numbers are very favorable."

Williamson said he liked Foles as a prospect, but he also thought Foles benefited from some favorable luck. "A few years ago, Josh Freeman got away with bad decisions and had a good touchdown-to-interception ratio, and Foles had a little bit of that last season," he said. "Right now, the perception is that he is better than he is. I have more faith in RG III or even Tannehill at this point."

Jake Locker (52.7): Polian placed Locker in a "be wary" category based on injuries and overall performance, but Williamson was more optimistic. "He is very interesting to me," Williamson said. "He runs, he can throw deep, he has tools and could become a Donovan McNabb type. He's a little hit or miss and probably will always have red-zone woes and accuracy issues, but he is a big, strong guy and I thought he played quite well last year. People assume the book has been written on Locker the way it was for Gabbert and Ponder, but I think he gets better all the time. Those other guys do not. With Ken Whisenhunt there and some receivers, I can see Locker becoming a good NFL quarterback."

Ryan Tannehill (50.4): "He is wired right and a great athlete, but I just never knew if he would be a quality quarterback," the GM said. "I saw him against Arkansas and he was playing so bad, they ran the ball back-to-back on third and fourth down, and lost the game. That soured me. That was saying he was not their best player." Polian said he thought the arrow was pointing up for Tannehill as long as the Dolphins' offensive line improves markedly. His early-career QBR score puts him in the same general range as Dalton and Locker, from which there hasn't been a ton of long-term success previously. Joe Flacco and Jay Cutler put up similar scores in their first 16 starts and went on to earn long-term deals, despite some questions about how good they really are. (Cutler is 15th out of 33 qualifying QBs with a 55.4 QBR score since 2006, while Flacco is 21st at 51.2.)

Cause for concern

Geno Smith (35.9): "The arrow was not really pointing up for him late last season, which tells us you should not bet the ranch on Geno, which the Jets are not," Polian said. "There are always outliers and I will not write the guy off until I get a better body of work. The numbers tell us to be wary. I saw some flashes, but I also saw a very unprepared QB. That is not a knock on the coaches. Smith was just unprepared to play at the NFL level. Ideally, he would not have been playing."