Having three head coaches in as many seasons has been a challenge for most of Oregon’s upperclassmen.

The coaching carousel has been an enjoyable ride for the veteran offensive linemen.

Three current starters recruited by Steve Greatwood, the program’s longtime offensive line coach now in his second season at California, have developed into outstanding players under Mario Cristobal.

The outcome of the 19th-ranked Ducks’ first road game of the season against the No. 24 Bears on Saturday at Memorial Stadium may be decided by which offensive line executes better against a dramatically improved defense.

“Awesome guy, great guy, Oregon legend … I love him like a dad,” left guard Shane Lemieux said of Greatwood. “It’s always good to go down and see him. Last year I saw him here. He made fun of my hair because I still had short hair back then.”

Greatwood was an assistant at Oregon for a total of 32 years, including 25 seasons as the offensive line coach, before Mark Helfrich and the long-tenured staff was fired after the 2016 season.

During the painful 4-8 finish, Greatwood started four redshirt freshmen — Lemieux, center Jake Hanson and tackles Calvin Throckmorton and Brady Aiello.

One of the most difficult losses for the Ducks that fall was the 52-49 double-overtime defeat at Cal, which was the first road start for true freshman quarterback Justin Herbert.

“I think we’re more physical, we’re a lot bigger, we’re a lot more confident,” Lemieux said of the unit’s development since the trip to Berkeley two years ago. “We were kind of thrown out there as redshirt freshmen. It was almost like an experiment, a case study. We were all out there messing around to see what happened.

“Obviously we were intending to win games, but I think it was more just looking to the future.”

When Cristobal was hired by Willie Taggart as Oregon’s new offensive line coach in 2017, he inherited four experienced redshirt sophomores and all-Pac-12 left tackle Tyrell Crosby, who missed the final nine games of the 2016 campaign because of injury.

After Taggart bolted for Florida State in December, the players signed a petition asking athletic director Rob Mullens to remove the interim tag from Cristobal’s job title.

Since being named the full-time head coach, Cristobal has remained heavily involved in working with an offensive line that still includes Lemieux, Hanson and Throckmorton in the starting five with Aiello rotating in as an unofficial sixth starter.

“You’re always pleased with the guys you have,” Cristobal said after Wednesday’s practice. “Those are really good football players. They’ve certainly grown a lot in the past year and a half, and we’re happy they’re here.”

True freshman Penei Sewell, the highest-ranked recruit in Cristobal’s 2018 class, is filling the void of Crosby’s graduation to the NFL as the starting left tackle. Alabama graduate transfer Dallas Warmack, who was recruited by Cristobal out of high school, is the starting right guard.

The Ducks controlled the line of scrimmage for the most part during their heartbreaking 38-31 overtime loss to No. 7 Stanford, piling up 524 yards of total offense on a defense that had been allowing 7.7 points per game.

“Obviously the tape doesn’t show the score. If you watch that tape offensively, I’d probably guess it’s like 30-zero,” Lemieux said. “We didn’t see the defensive side. But watching us you’d think we won that game, and the scoreboard didn’t show it.”

Greatwood’s offensive lines paved the way for Oregon’s streak of 10 consecutive seasons (2006-15) leading the Pac-12 in rushing.

Cal returns all seven players who made starts on the offensive line last season, including left guard Valentino Daltoso, who transferred from Oregon after Greatwood was hired by head coach Justin Wilcox.

“They do a heck of a job, they really do,” Cristobal said of the Bears’ offensive line. “We’re very familiar with some of those guys, we’ve recruited a bunch of those guys as well. And one of our former players is there, in Vinny Daltoso, doing a great job for them.”

The Ducks (3-1, 0-1) lead the Pac-12 in scoring (46.5 ppg) and are second in yards per game (508.3) and rushing yards per game (205.0). The Bears (3-0, 0-0) are sixth in the conference in scoring (30.0 ppg), ninth in total offense (382.3 ypg) and fifth in rushing (180.0 ypg).

“They’re really good,” Oregon defensive coordinator Jim Leavitt said. “They’ve got four guys back (on the offensive line) that had all started last year. So they’re a veteran group as far as that goes. They know what they’re doing, they’ve been in the system two years now and they play hard.

“They’re undefeated for a reason.”

There will be mixed feelings during Saturday’s reunion. The Ducks’ older offensive linemen miss Greatwood but also love playing for Cristobal.

“They are definitely different personalities for sure and both great offensive line coaches,” Hanson said. “I still have a tremendous amount of respect for coach Greatwood because he taught me so much and helped me develop in the two years I was here with him. They are different guys, coach Wood is more of an old-school guy.”

Cristobal believes strongly that this new era of Oregon football begins with physical play at the line of scrimmage. The Ducks should have delivered a signature win for the first-year coach after pushing the reigning North Division champions around for about 56 minutes.

“I came here for coach Greatwood recruiting-wise, but I think it all worked out in the end,” Lemieux said. “Because now I have an O-line coach who is a head coach. That’s pretty rare.”