"Our linebackers will be very fast," Petrino said. "We're working to find out who will be the three best guys to get on the field."
Returning to lead the unit is middle linebacker Nate Harris, a 6-2, 230-pound senior. Harris made 66 tackles and seven sacks last season after transferring from junior college. He figures to have a stranglehold on a starting job, but he'll certainly be pushed by sophomore Lamar Myles, who made his first career start against Oregon State last season.
"We return Nate Harris and Lamar Myles in the middle," Petrino said. "Both of them did a great job against the run, and in our blitz package last season. They're both still working to understand our pass defense, though."
Petrino said he'll make one subtle change at linebacker before the Cardinals begin spring practice, moving returning starter Abe Brown from the strong to the weak side. That move will allow junior Malik Jackson to step into the first unit at Brown's former position.
"We've swung (Abe) over to the weak side, and put Malik Jackson at the SAM (strong side) linebacker position," Petrino said. "Both of them played a lot last year. I thought Malik played real well when Abe got injured. And we still have Preston Smith, who started a few games and did a nice job there."
Petrino's also counting on junior special teams stalwart Terrance Butler to compete for a spot in the two-deep, and push the returning starters for playing time.
"I think this is the time for Terrance Butler to really make a run at one of those linebacker positions," Petrino said. "He was our leading tackler on special teams, and was one of the guys who showed the most speed and ability to tackle. So he's going to put pressure on those guys, and he wants to take somebody's position."