Mark Jackson is starting to get comfortable.
The junior defensive end/linebacker and starting JACK has been a consistent part of Oklahoma's defense so far this season after playing in 13 games last season but never starting.
"It was a new experience definitely, at first," Jackson said. "But I've started to become accustomed to it as the weeks go by and started to really settle in."
Last season, Jackson was the backup at the JACK position, behind now-Los Angeles Rams linebacker Ogbonnia Okoronkwo. He and Okoronkwo grew close in that time, and Jackson learned a few things from him.
"Being patient, being consistent and playing for the team," Jackson said.
The 6-foot-1-inch Jackson has been playing more consistent, defensive coordinator Mike Stoops said. Jackson has always been athletic, and the opportunity to play more has helped him grow.
So far this season, Jackson has emerged as a consistent part of Oklahoma's defense, picking up at the JACK where Okoronkwo left off. He's recorded 18 total tackles and 1.5 sacks through three games.
"It's been key," Riley said of Jackson's development. "Especially with the whole situation with Addison Gumbs with the injury and then the transfer, and the fact that we had some youth there and replacing a really, really good football player from the last couple years. And that position has been a strength for our defense for a long time now."
When the Sooners released their first depth chart of the season, Jackson or Gumbs was listed as the starter, but when Gumbs got injured before Oklahoma's game against Florida Atlantic, Jackson found the starting role to himself and hasn't looked back since.
"I think he's got a big upside, and hopefully he finally realizes the player he should be," Stoops said. "He's still young ... He's kind of coming into his own as a player."
The Cibolo, Texas, native didn't see the field much in his first two seasons with the Sooners, recording a total of nine tackles. Last season, Jackson recorded his first career sack against Ohio State and forced a fumble against Kansas backing up Okoronkwo.
"Mark's done a really nice job," Riley said. "We've been pleased with the way he's played up to this point. He's been physical. He's held up in the run game. He's always had pretty strong ability as a pass rusher, and as he's taking all the snap that he is, I think he's getting even more comfortable and loose and able to play more athletic, which he is.
"He's done a great job — he really has — and the fun thing for him is he can play a lot better."