Tyrell Crosby started for the Ducks in the national championship game as a true freshman.

The current Detroit Lions offensive lineman didn’t crack the starting lineup until the third game of his Oregon career. Crosby mostly played right tackle during the 2014 season with Jake Fisher charged with protecting Heisman Trophy winner Marcus Mariota’s blindside.

Now another young prodigy, Penei Sewell, is filling Crosby’s sizable shoes as Oregon’s new starting left tackle.

“Shoes he will quickly outgrow,” Crosby predicted on social media.

Sewell, who doesn’t turn 18 until next month, was the first true freshman to start a season opener on Oregon’s offensive line since Lee Gundy in 1997.

Protecting Justin Herbert isn’t too weighty for the 6-foot-6, 345-pound phenom from St. George, Utah.

“I get that question a lot. It’s pretty big,” Sewell said of the responsibility. “Justin Herbert is a very, very big Heisman candidate. He’s a good player. I just don’t think about that stuff. I don’t like to create more pressure for myself. I just go out and play.”

Oregon coach Mario Cristobal, whose fingerprints are still all over the offensive line, said he has graded Sewell out in the “high 80s” during the first two games.

Sewell and left guard Shane Lemieux led the team in knockdowns during the Ducks’ 62-14 steamrolling of Portland State.

“He’s a creature, man, there’s no doubt about that,” Lemieux said of the new road grader lined up on his left shoulder. “The first day I saw him this summer, it was just shorts and spider pads, it was like, ‘OK, this guy is legit.’

“I don’t know what Tyrell looked like as a freshman, but he’s got to be that or better.”

During fall camp, Cristobal also considered Calvin Throckmorton, Brady Aiello and George Moore for the top spot on the depth chart at left tackle.

Sewell had never played the position before.

“In fact, I think he’ll be the first to tell you when he had a couple of reps at some of those events they have nowadays, those recruiting events, it wasn’t a great couple of reps for him,” Cristobal said.

It didn’t take long for Sewell to get up to speed, which allowed Throckmorton to remain at right tackle and for Aiello, who filled in for an injured Crosby in 2016, to be a sixth “co-starter” in the offensive line rotation.

“Everybody had some pretty significant success, it just seemed that (Sewell) was feeling more and more comfortable,” Cristobal said. “He was being very productive in the sense that he was playing with a lot of power, a lot of balance and body control. Really just doing a good job of controlling defenders at the line of scrimmage and knocking people back. So the decision was made. …

“You’re looking at a 17-year-old guy, so you always want to see how that works out. But he doesn’t flinch, and we think he’s just scratching the surface as to what he’s going to be.”

Sewell didn’t find out he would be starting at left tackle until the offensive line meeting a couple of days before the opener against Bowling Green.

Two weeks later, Oregon’s offense is averaging 60 points and 533 yards entering Saturday’s game against San Jose State at Autzen Stadium (2 p.m., Pac-12 Networks).

“High,” Sewell, who chose the Ducks over Alabama and USC during the recruiting process, said of his expectations entering his first collegiate season. “I just wanted to jump in on what Cristobal is building here. I trusted in him and wanted to be part of the Oregon football program.”

Starting as a true freshman means Sewell is going to be an important part of the Ducks’ success for at least three seasons.

That’s an exciting development for classmate Travis Dye, who ran through a gaping hole created by Sewell and Lemieux and went untouched on a 49-yard touchdown against the Vikings.

“The first two days he came out here and he was out here pancaking grown men,” Dye said when asked when he knew Sewell was a special talent. “It was just, yeah, he’s here and he’s ready to play. He’s very mentally up there. He knows what he’s doing.

“I can’t wait to run behind him for years to come.”

After making his first start against Bowling Green, Sewell joked that he had reached out to Crosby but the NFL rookie “wouldn’t hit me up.”

There was a conversation between the big men, and Crosby’s advice was simple.

“He just said, ‘Be you. Coach Cristobal recruited you for a reason, so just go out there and do what you do,’” Sewell said.