Trevathan, a breakout star in 2013, revealed Wednesday that he underwent kneecap replacement surgery in January.
Trevathan is adjusting to the new kneecap because it's slightly bigger than the faulty one with which he entered the world.
"I wish we had gotten (the surgery) done sooner," Marshall said. "I'd be a lot further along."
Although both linebackers are on the right track, the coaches will work with the medical staff to ease them into training camp.
They are loaded on the defensive line, at edge rusher and in the secondary. The big question is whether Trevathan and Marshall can recapture pre-injury form early in the season.