Tanner Brock, who was sidelined last season with an ankle injury, was likely the Frogs’ best overall player and certainly was expected to be an all-Big 12 candidate at linebacker. He’s gone, and so is Devin Johnson, a starter at safety the last seven games last year who would’ve been a veteran presence in a young defensive backfield. The linebacker unit suffered another loss when Deryck Gildon, expected to replace Brock, left the team. And, at last check, cornerback James Bailey has been removed from the team’s online roster.

But then there’s the defensive line. The Frogs’ front four lost starting defensive tackle D.J. Yendrey, but Yendrey’s absence shouldn’t be as detracting as Brock’s or Johnson’s of Gildon’s.

Stansly Maponga, the all-American candidate who earned preseason all-Big 12 honors, and Ross Forrest, the overachieving walk-on out of Odessa Permian High School, both represented TCU Monday at Big 12 Media Days in Dallas. Maponga and Forrest are returning starters, playing opposite of each other, and both should anchor a defensive line that, despite the loss of Yendrey, should be strongest section of the Frogs’ defense.

Jon Lewis, Chuck Hunter and David Johnson all return at defensive tackle. Johnson suffered an injury late in the year, but all three saw extensive roles in 2011. And coming in is four-star defensive end Devonte Fields, an Arlington Martin product who could compete for playing time.

“We lost a few guys, but with the young defensive lineman that have come in, I’ve taken it has an opportunity to teach them some things,” Forrest said. “The good part about those guys is they’re all willing to learn. That’s huge for us.”

Success in the back of the defense can’t happen without the front line doing its job, Maponga said.

“We have to cause pressure,” Maponga said. “If the whole defensive line causes pressure, it makes it easy for our secondary to do their job. So it’s got to start out with us.”

In the spring, TCU coach Gary Patterson called on Maponga to step more into a leadership role.

“I can see where he’s coming from, and I needed to do that and I’ve done it,” Maponga said. “Since I’m a leader on the team, I’ve been taking care of the young guys, making sure they grow up, making sure everything they’re doing is right.”

Maponga has also centered his attention on improving his own game, watching film of games from last year, something he did in between his sophomore and freshman season, when he earned freshman all-American honors in 2010.

“I watch film of my own games,” Maponga said. “I wasn’t disappointed, but they haven’t seen the best of me.”