Left tackle R.J. Dill has helped the Terps cover for an ailing offensive line.

When Terrapin offensive lineman R.J. Dill saw teammate Justin Gilbert fall to the ground and clutch his left knee against West Virginia on Sept. 18, his first thought was innocuous enough.

“I hope it’s just a cramp,” Gilbert remembered thinking.

An MRI revealed much worse. Gilbert had torn his ACL in the loss to the Mountaineers, ending the left tackle’s season and dealing a major blow to an offense with a dearth of experienced backups on the line.

“It’s a tough situation, why I’m over there,” said Dill, who started the Terps’ first three games at right tackle and was forced to switch to left tackle when Gilbert went down nearly a month ago. “No one would want to be in the situation I’m in, where you have to fill in for one of your best friends.”

Roommates in their first years with the team, Dill and Gilbert have remained close, both as friends and in their development on the field. Last year, as redshirt freshmen, both saw action on the team’s starting unit. Dill moved into the lineup at right tackle early in the year, while Gilbert took over after injuries forced him into the rotation later in the season.

This year, Dill and Gilbert, measuring at 6-foot-7 and 6-foot-6, respectively, and weighing in at 300 pounds apiece, were set to serve as imposing bookends for a long-beleaguered Terp offensive line.

Since Gilbert’s crippling injury, though, Dill’s game has done a 180. The lineman had played on the left side for three weeks in spring practice as a true freshman, but never again thereafter.

That was until Sept. 18. His friend’s moves, once seemingly mirror images, are now his own.

“Everything’s backwards,” Dill said. “But it’s an opportunity for me to get better and expand what I do. It’s just doing extra things, staying after, working on my pass protecting at left tackle and working on my steps.”

Some linemen, such as former Terp and current Washington Redskin left tackle Stephon Heyer, have the natural ability to switch sides seamlessly. But players with those instincts — much less, as redshirt sophomores — are rare.

“People say it’s got to be real hard to move from left to right and right to left, and I think only guys who are really technique-savvy can do stuff like that,” said center Paul Pinegar, who also has filled in as the team’s starting left guard. “But I think [Dill] is really sound in his technique.”

Still, even with an able substitute in Dill, the loss of Gilbert midway through the West Virginia game threw the Terps’ already struggling offensive line further off track. The team gave up three sacks before Gilbert left the game and five more after, and ended the game with minus-10 rushing yards.

The next week, coach Ralph Friedgen went to Dill and redshirt freshman Pete DeSouza, who had moved into Dill’s starting spot on the right side, with a forceful message.

“You’ve got to show up,” Friedgen told them. “What are we going to do? We lost our left tackle — are we going to go home, take our ball and go home? Or are you going to fight? … They saw a side of me they probably haven’t seen.”

Even as the quarterback behind it varied, the new-look line held firm, especially in pass protection. The unit surrendered just one sack in a victory over Florida International, and it held Duke without any last Saturday.

“Dill knew he had to step up to fill Gilbert’s shoes, and he has some big shoes to fill because he’s a heck of a player,” running back Da’Rel Scott said. “But just seeing that unit, knowing that they had to step up, just proved my confidence in the line. They raised their games to make it seem like nobody really got hurt.”

The line is still looking to afford Scott and the Terps’ stable of running backs the same help. After allowing the Terps to rush for 261 yards, their highest rushing total since 2008, in the season opener against Navy, the offensive line has struggled to open up holes of late. Against a woeful Duke rushing defense, the Terps rolled up 124 yards but did so on 39 attempts, good for a mere 3.2 yards per carry.

“We’ve got to be able to impose our will,” Dill said. “We’ve got to be able to line up and even when everybody in the world knows we’re going to run the ball, we need to be able to run it.

“I’m not going to rest on my laurels, and I don’t think the rest of this team will,” Dill added. “I don’t think that’s what we’re made of.”

TERP NOTE: The Terps will wear specially designed uniforms to honor the U.S. Armed Forces as a part of Under Armour’s Wounded Warrior Project. The Terps will don camoflage uniforms and cleats in their game against Florida State at Byrd Stadium on Nov. 20.

kyanchulis@umdbk.com