Conor McDermott has grown into a starring role on UCLA’s offensive line

Conor McDermott engages in a role reversal every time he protects Josh Rosen from defenders charging from the quarterback’s blind side.

For much of his career, McDermott was the one no one saw coming.

UCLA’s massive left tackle appeared to be more likely to play in Pauley Pavilion than in the Rose Bowl until only a few years ago. He was Tennessee’s Mr. Basketball in high school and didn’t even send out tapes of his football highlights until after his senior year, when the Bruins finally recruited him as an undersized tight end.

Girth is no longer an issue for someone who resembles a mid-career NFL lineman.

At 6-feet-8¾ and 310 pounds, his hair already thinning a bit, McDermott will take the field in the Bruins’ season opener against Texas A&M at Kyle Field on Saturday as his team’s largest and perhaps most significant player besides Rosen.

He’s also the eldest Bruin, a designation none of his teammates can contest.

“They all know I’m an old man,” quipped McDermott, who turns 24 next month.

McDermott will put his own twist on a kid’s game against the Aggies, playing keep-away with Myles Garrett. The star defensive end is projected as the possible top pick of the 2017 NFL draft and has targeted 20 sacks as his goal this season, a pursuit McDermott hopes to impede as much as possible.

The challenge of getting around McDermott figures to be daunting. His combination of long arms and quick feet, in addition to all that bulk in between, makes him ideally suited to prevent even the most agile pass rushers from reaching their intended destination.

“They don’t grow those guys on trees,” UCLA Coach Jim Mora said. “We’re trying.”

Rosen’s reaction upon learning that McDermott was putting off the NFL to return for his senior season said everything about the tackle’s value to the Bruins. Rosen burst through a door inside McDermott’s apartment, wrapped him in a hug and repeatedly thanked him.

“We were all thrilled,” Rosen said. “We went out to B.J.’s for dinner.”

Mass consumption has been a necessity for McDermott since he arrived in Westwood four years ago as something of a lightweight. The only opponents he dominated then were of the shirts and skins variety in pickup basketball games inside the old Wooden gym.

“Eighty pounds ago and I was dunking it,” McDermott recalled, “which I still can.”

Basketball had been McDermott’s passion at the Ensworth School in Nashville, where he starred on a state championship team and was selected Tennessee’s Mr. Basketball for Division II-AA. He played tight end and tackle on offense and defense for the football team but didn’t generate interest among colleges until late in his career.

Virginia Tech offered a scholarship, which UCLA matched in part because of the presence of McDermott’s brother Kevin, the Bruins’ long snapper, who now plays for the Minnesota Vikings.

“I guess when the Virginia Tech one came, the UCLA coaches were like, ‘K.P., you didn’t tell us about your brother,’ ” said McDermott, who spent a year at a prep school in Connecticut rehabilitating a shoulder injury before heading west.

Rick Neuheisel, who coached the Bruins at the time, pegged McDermott as a tackle, meaning he needed to pack on the pounds once he reached campus. His struggles with weight were the opposite of most students fighting the so-called freshman 15.

Frustrated by his high metabolism, McDermott would sigh every time Courtney Morgan, then the Bruins’ director of player development, inquired about his progress. But his fridge-emptying appetite eventually was reflected on the scale.

“He eats six, seven times a day and has always been like that,” said Deborah McDermott, Conor’s mother. “I went through gallons and gallons of milk with my boys. They would have a jug of their own and sometimes it never made it to the glass.”

By springtime of McDermott’s freshman year, the numbers began to creep upward. He reached 250 pounds, then 265, 275, 285. By last fall, as a fourth-year junior, he weighed 320 before dropping 10 pounds to his current weight. Mora said McDermott’s frame is probably capable of carrying as many as 330 pounds in the NFL.

McDermott inquired about his draft stock after last season and was told he could go as low as the fourth round even though he had been part of an offensive line that yielded only 14 sacks in 2015, the second-lowest total in school history. The fact that McDermott had played just one full season of college football led to some hesitancy among teams, prompting his return.

But coming back was every bit as much about McDermott’s teammates as it was about him. Some long talks with his parents convinced him that one more year of college would allow him to develop into the leader he never could previously become as someone who had spent his entire football career up and coming.

He’s here now, and if all goes well Saturday, he’ll be immovable.

ben.bolch@latimes.com

Twitter: @latbbolch