Reilly will start at right defensive end in place of Joe Kruger when the Utes are in their nickel package, and he'll start at stud, or strong side linebacker, when they are in the 4-3.
He played both positions last year and finished tied for 16th in the Pac-12 in tackles for loss and tied for third in the league with four forced fumbles.
His best game came against BYU, when he had five tackles, three tackles for loss, two sacks, three forced fumbles, a pass breakup and a fumble recovery.
As disruptive as he was, though, Reilly said switching from end to linebacker hurt his game at times.
"I wasn't totally prepared for it," he said of the adjustment. "It was a good season, but at times I kind of felt caught in the middle."
This year he feels more prepared, having added 20 pounds to his frame and spending most of the summer working on his technique.
"I feel faster and stronger," he said. "We worked a lot with bag drills, getting our hands stronger and things like that. It seems kind of like an odd thing to do, but it works."
"Odd" is often the way Reilly is described by his teammates. It seems he is always up to quirky things, such as the time in 2004 when he set a world record for onion eating by devouring a 7.5-ounce onion in 1 minute, 35 seconds.
Athletically, he didn't always follow the traditional path of football players, opting to play volleyball in addition to basketball as a high schooler.
While some fear playing multiple sports will hurt their chances of excelling in one, Reilly's career was only helped by the experiences. All the techniques and nuances of the various sports have helped him become a multifaceted player.
"He is going to be just awesome," Utah defensive coordinator Kalani Sitake said. "I've always been high on him as a player, and it's obvious from what he did last year that he has some amazing tools. There is a confidence about him that helps him. If there is any hole in our defense, inside linebacker, safety, we could put him there. His pass-rushing skills are unbelievable, and with his frame he creates a lot of mismatches."
Reilly credits at least part of his confidence and maturity on the field to his life off the field. Reilly served an LDS Church mission in Sweden before joining the Utes, and he is married with a daughter, Nelli Ann Marie.
"All that has made me more of a mature human being," he said. "They always talk about what you do carries on and off the field, so I think that has made a difference for me."
He and his wife, Jessica, are expecting another daughter on Sept. 22, the day Utes play at Arizona State.
"She's a trooper. I know she can hang on for one more day so I can be home," he said. "Then we've got that week off, so I can spend that time with them. It fits perfectly."
Much like Reilly's place with the Utah defense.
Trevor Reilly file
• 6-foot-5, 245 pounds, Junior
• From Valley Center, Calif.
• 22 percent of his career tackles have been for loss
• Tied for third in the Pac-12 with four forced fumbles in 2011
• 76 tackle-for-loss yards is tied for the eighth-best single-season total at Utah