San Francisco 49ers

49ers say they have to be aware of A.J. Jenkins’ speed

After the 49ers shipped A.J. Jenkins to Kansas City last August, coach Jim Harbaugh said there was no reason to think the young wide receiver wouldn’t have “a great career” with the Chiefs.

It’s safe to say that Harbaugh hopes that career doesn’t suddenly take off Sunday.

Jenkins, whose only season with the 49ers ended without a catch, will get a chance to show his former team it gave up on him too soon. He is in line to start Sunday’s game at wideout after Kansas City’s regular starter, Donnie Avery, was diagnosed with a sports hernia.

The 49ers last year traded Jenkins, their first-round draft pick in 2012, to the Chiefs for receiver Jonathan Baldwin, who also was a former first rounder. Baldwin made no impact and was released this season.

Jenkins started in Week 17 last year while the Chiefs rested their starters in anticipation of the playoffs. He had three catches for 67 yards, by far the best outing of his young career.

“I can’t get too caught up in that kind of stuff, because I’ve got to be focused on what I’ve got to do,” Jenkins told reporters in Kansas City. “I’ll be ready for Sunday, but I’ll even be more ready if I’m not concerned about what’s going on out there this weekend or who we’re playing against. I’m not worried about San Francisco. I’m trying to get my playbook right.

“But it is crazy how things work out,” he said. “My first start will be against the team that traded me. Things happen for a reason.”

Jenkins has been averaging 12 snaps a game this season and has four catches for 16 yards.

“He was here and some of the guys know him,” 49ers safety Antoine Bethea said. “He’s a speed guy. He can take a top off of a defense, so we have to be aware of that. And coming back, just like Alex (Smith), he’s going to want to have a (good) game. So we have to be aware of that.”

Harbaugh vigorously defended Jenkins both during the receiver’s lackluster rookie season – he didn’t catch any passes that year – and after he was traded. The 49ers coach said Friday that he sees progress from his former pupil.

“I believe he’s continued to grow as a player,” Harbaugh said. “He’s also on the field-goal (and) extra-point block (units) coming off the edge, and he’s gotten close a few times. We’re aware of him and need to be.”

Nicked nose – Nose tackle Ian Williams, whose strong play helped fuel the 49ers’ win over the Eagles on Sunday, was a late addition to the team’s injury report. After practicing Wednesday and Thursday, Williams sat out Friday’s session with an ankle injury.

Linemate Justin Smith noted that opponents have targeted the middle of the 49ers’ defensive line in their run game, but haven’t had much luck. The 49ers rank second in run defense through four weeks.

“Trust me, teams are trying to run directly at him,” Smith said of Williams. “They’re not getting the movement on him that they want. That’s why they’re going to the edges. He’s strong at the point and he’s fast at pursuing. That’s what makes him a really good nose.”

Et cetera – Williams and four other starters – cornerback Tramaine Brock, offensive tackle Anthony Davis, tight end Vernon Davis and safety Eric Reid – are listed as questionable. Vernon Davis said there was a “small chance” he would play against the Chiefs.

No 49ers were fined by the NFL for penalties incurred during last Sunday’s game against the Eagles, the first time that has happened this season. The 49ers lead the league with 46 penalties.

Carmichael’s Chase Dinaburg, 7, will be the “kickoff kid” at Sunday’s game. Chase will be responsible for retrieving the tee after the opening kickoff. He plans to wear his No. 15 Michael Crabtree jersey.