Stanford's scoring average surged from 23.8 points per conference game in 2014 to 40.9 in 2015, a 17.1-point increase that pushed the offense's rank from 11th in the Pac-12 to the very top spot.

Christian McCaffrey and Kevin Hogan earned the headlines behind this massive jump in productivity. And that's understandable: The former is the new NCAA's new single-season record-holder in all-purpose yardage, and the latter ranks among the top five nationally in both quarterback rating and yards per attempt.

But there's another component of Stanford's attack that's made a colossal surge in 2015, and it shouldn't be disregarded: After a yearlong hiatus, the Cardinal's offensive line is again the unit's beating heart.

"We had linemen playing at an extremely high level," head coach David Shaw said. "All four guys who started last year were better this season. They all played their best football with another year of experience."

Guard Joshua Garnett won the Outland Trophy, given to the country's best interior lineman. Fellow senior Kyle Murphy has anchored the left tackle spot with top-level precision, while center Graham Shuler, right guard Johnny Caspers and right tackle Casey Tucker -- the unit's only new starter in 2015 -- have all combined to fortify a line with two superstars on its left side.

The result has been the dominant offensive line that Stanford envisioned back on national signing day in 2012, when they inked three five-star hogs at the position and circled 2014 and 2015 as the seasons in which they'd be physically mature enough to wreak havoc. Shaw touted the line's potential effusively before last season -- "they have a chance to be the best in the country" -- but that didn't come to fruition in 2014, as mistakes and a lack of cohesion led to the Cardinal's worst rushing performance (4.3 yards per carry) since 2007.

But in 2015, Shaw's words have become prophetic: The Cardinal's 5.1 yards per carry are on par with the Toby Gerhart and Stepfan Taylor-fueled golden age of running the football. And as a result, the "Tunnel Workers Union" moniker, first coined when Jim Harbaugh tried to implement a blue-collar mentality in the line, is back in full strength.

Players and coaches agree that the turning point was Stanford's season-opening 16-6 loss to Northwestern, in which the offense averaged only 3.9 yards per play as the line made a bevy of mistakes. From that point forward, the unit made a commitment to not repeat 2014.

"Afterward, we all had that sick feeling in our stomach because it felt like last year when the D was carrying our backs the whole way," Murphy said. "But we knew it wasn't destined to be that way this year. We knew that we were way better than that. It was a fluke. We knew that we were going to be able to turn it around. We weren't going to be denied."

There was some shakiness the following week, too -- the unit committed three first-quarter penalties -- but Shuler credits Hogan's steadying presence behind center for helping right the ship.

"He had faith in us the whole time," Shuler said. "He pushed us and trusted us. He was pressured in that UCF game, but he stayed in the pocket. That was reassuring for us."

The Cardinal took that reassurance and used it to deliver a methodical tour de force in a 41-31 win at USC their next time out. They churned out over 40 minutes of possession, powered through multiple critical third downs, and set the tone for the rest of a dominant year.

"Confidence is great," Shaw said. "You have a runner making you right even if you're not perfect, and things start to jell. After that Northwestern game, we played as well up front as anybody in the nation."

That runner, of course, is McCaffrey, the super sophomore who was quick to commend his blockers in virtually every interview during his historic campaign. But praise on this Stanford team is like a hot potato -- it's difficult to find a player or position group that'll toot its own horn too loudly.

"Christian and Kevin have made our jobs a lot easier, that's for sure," Shuler said.

So credit is usually deflected elsewhere. Still, there's a healthy hunger for attention present in this offensive line, especially whenever Garnett's road-grading heroics -- which took social media by storm after a screen pass against Washington -- are discussed.

"I was a little bitter because I pancaked someone on that play too and no one said a word about it," Shuler laughed.

There's a friendly competition among these linemen centered around who can deliver the greatest volume of flattening blocks. Perhaps that's provided the fire that's unlocked Stanford's potential up front this year.

"We came in looking to do something special as a group," Shuler said. "We weren't going to be denied doing that. And after that first loss, we were frustrated. So we did everything we could with our backs against the wall to make it happen."