Can the Celtics win 50 games?

ESPN Insider Kevin Pelton and real plus-minus developer Jeremias Engelmann discuss expectations for the Boston Celtics, who are projected to compete for the second seed in the Eastern Conference. But do the Celtics have a star? What are the reasons for concern? Can they win 50 games and the Atlantic Division?

Why is RPM high on the Celtics?

Kevin Pelton: If there's one 2015-16 team projection based on ESPN's real plus-minus that's likely to surprise readers, it's how high RPM is on the Boston Celtics. Based on my projections for playing time, the Celtics come out expected to win 48 games -- the second-best projection in the Eastern Conference, after the Cleveland Cavaliers.

Given that Boston was pegged for 40 wins by the ESPN Forecast panel this summer and started with a line of 42.5 wins at the Westgate Las Vegas SuperBook, it's safe to say that RPM is far higher on the Celtics' chances than conventional wisdom.

(The same can be said of other statistical projections, including FiveThirtyEight's CARMELO system, which incorporates RPM, and projections by Andrew Johnson and Nathan Walker on Nylon Calculus.)

To try to understand why Boston looks so good, RPM creator Jeremias Engelmann joins me to discuss the projection. So, Jerry, what is RPM seeing in the 2015-16 Celtics?

Jeremias Engelmann: First, I want to say that I'm actually surprised that anyone would put them as low as 40 wins. They had a point differential of plus-3 after the All-Star break in no small part due to the arrival of Isaiah Thomas, who averaged 26.5 points and 7.5 assists per 36 minutes for them.

Given that each surplus point of a team's point differential translates to roughly three additional wins, we should expect them to win about 49 games based on last season alone.

RPM thinks they're a really deep team: nine of the 11 players pegged to be in their regular rotation have a positive RPM, with the only negatives being Evan Turner and David Lee.

Except for the latter, everyone is on the good side of 30, with the majority of them being younger than 25. As such, many of their players are expected to take a step forward from last season.

Pelton: In defense of the Forecast panel, they're not wrong to be skeptical about second-half improvement. Earlier this week, Matt Pacenza of Salt City Hoops found that over the last decade teams whose winning percentages improve as dramatically as the Celtics (and the Indiana Pacers and Utah Jazz last season) tend to give back nearly all that improvement the following season.

But Boston literally was not the same team after the All-Star break because Danny Ainge made somewhere between seven and seven hundred trades last seaspn. (OK, it was seven.) Thomas was the single biggest addition, but Jae Crowder was an important contributor and the Celtics also got nice minutes from Jonas Jerebko. How much better is this Boston team than the one that started last season?

Engelmann: Beyond last season's additions, predictive RPM is a way bigger fan of Amir Johnson (plus-3.9) than departed Brandon Bass (minus-2.5), explaining part of their projected bump in wins.

And going back to last season, some of the projected improvement also stems from the fact that Rajon Rondo is not on the roster anymore. Thanks to his now truly abysmal true shooting percentage -- his 2014-15 season ranks as one of the bottom 20 seasons for guards since 2004 -- Rondo just hasn't been a positive difference-maker since tearing his ACL in 2013. Just ask the Dallas Mavericks.

For the Celtics those minutes will go to 21-year-old Marcus Smart, the rookie with the best RPM in 2014-15.

The more I think about this team, the more I like the over.

Do the Celtics have a star?

Pelton: Let's talk a little about Smart. So much of the conversation about the Celtics centers on how they can get a "star." Given how inefficient he was offensively as a rookie, Smart is unlikely to fit the conventional definition of that kind of player any time soon.

But he was so good defensively that he still rated just outside the top 10 point guards in the league by RPM last season, and we'd expect rapid development as a scorer in year two. Can Smart be their star?

Engelmann: It's true that Smart posted worrisome shooting percentages in his rookie season, although that didn't seem to hurt their offense a lot (their offensive rating was four points better per 100 possessions with him on the court).

I don't think he can be a traditional superstar point guard like Stephen Curry, Russell Westbrook or Chris Paul, but I like to compare him to Kyle Lowry and Eric Bledsoe, who posted similar numbers at similar ages, including the not-so-great shooting percentages. These are guys you hate to play against because of their pesky defense, they are solid contributors to their team's offense and they post good plus-minus numbers year after year.

Will Smart be a star in coming years? He'll most likely not be part of the elite, but he'll be right there in tier two.

Given that their most gifted scorer, Thomas, will most likely come off the bench, it seems like the team will have to do without a traditional star -- a feat just recently accomplished by last season's Atlanta Hawks.

Should we be skeptical of the Celtics?

Pelton: What reasons do you see for skepticism about our projection for Boston?

Engelmann: One area of concern is that they only have one good shot creator in Thomas, who led the team last season in both points and assists per minute while having the second-best true shooting percentage on the team.

Many of their players, including Smart, Crowder, Avery Bradley, Evan Turner and Jared Sullinger, aren't great at creating efficient shots for themselves. If Thomas goes down or has to play with a nagging injury -- he has missed some time in training camp with knee tendinitis -- their offense could be in trouble.

Pelton: That's a place where I think Smart's development could be crucial in terms of giving the Celtics a few more options. Before Thomas' arrival, they relied heavily on Turner as their primary creator despite the fact that, as you note, he has never been efficient in that role.

And that's the other concern I'd mention. As many players as Boston has that rate well by RPM, the two rotation members who don't project as average or better -- Turner and Lee -- both might end up starting and playing more minutes than statistical analysts might prefer. We'll see whether Brad Stevens adjusts if those projections prove accurate.

We sort of started by talking about how much we believe in the projection vis-a-vis other expectations, but to wrap things up let's revisit that question. How many games do you expect the Celtics to win this season, and how realistic is it that they can win the Atlantic Division or even finish second in the East?

Can the Celtics win 50?

Engelmann: I think high 40s is realistic, with even 50 wins being possible. But the second tier in the East, after Cleveland, isn't exactly a clear-cut picture: No fewer than seven teams have been projected to win 44-plus games by either RPM or Vegas.

Vegas leans more toward Atlanta to be the second-best East team, and Chicago should make a strong case, as well.

With Toronto probably being a bit weakened from losing Johnson, Lou Williams and Tyler Hansbrough, and no other Atlantic team posing a threat, I give Boston a better-than-50 percent chance to win their division.

But simply due to the large number of Eastern teams vying for the second spot -- a situation in which one unlucky bounce can drop you several spots in the standings -- their chances of finishing second, even with how good we except them to be, probably aren't much better than 20 percent.

Pelton: Fifty wins would be close to a best-case scenario, but given how much Boston's depth should help over the course of the long regular season I certainly think it's possible. In fact, the original run of RPM projections had 51 wins as a baseline for the Celtics before I added a factor regressing the projections to the mean that took them down to 48. (The original, loftier projection was referenced in Tom Haberstroh's Boston preview.)

That change doesn't dramatically alter the Celtics' chances of finishing second in the East. And even if they're only about 20 percent, well, that's 20 percent better than most of the world is giving them!