49ers cornerback scenario revolves around Tramaine Brock's health

SANTA CLARA, Calif. -- Jim Tomsula was fine, thank you very much, with revealing his starting offensive line heading into Thursday night's preseason finale against the San Diego Chargers at Levi's Stadium.

Marcus Martin was moving from right guard to center for the San Francisco 49ers and the recently acquired Jordan Devey was, somewhat shockingly, going to start at right guard.

Transparency ... and whatnot.

But query the 49ers coach about the second starting cornerback opposite Tramaine Brock, and well, ask at your own peril. At least, that's how it went down Tuesday.

"Yeah, we're not going to talk as in depth there," Tomsula said.

"I'm not going to get into that too much."

The reason being is that Brock tweaked a hamstring during the second of two joint practices with the Denver Broncos last Thursday and did not play in the exhibition Saturday night, nor is he expected to play tonight. It leaves a question mark over the position.

Especially since Brock, who was limited to three games last year due to toe, ankle and hamstring issues, has also been the 49ers' slot cornerback.

Kenneth Acker had an impressive outing in Denver, picking off Peyton Manning in the end zone and breaking up another would-be touchdown pass.

But he also had a boneheaded move when he flipped the ball away in celebration after the pick, but before being touched down. And yes, he's taken some ribbing in his locker room.

"That's OK," said Acker, who missed last season with a foot injury, "I've got thick skin.

"In my mind, I'm here. I'm feeling like this is somewhere I can grow."

Then there's Acker's draft classmates, Keith Reaser, who sat out last year rehabbing a torn ACL, and Dontae Johnson, who played all 16 games last season, started three and picked off the St. Louis Rams' Austin Davis as a rookie.

Shareece Wright, who signed as a free agent after four years and 27 starts with the Chargers, entered training camp as the starter but has seen fewer reps with the first-team defense of late.

The decision, it seems revolves around Brock's health, because if he can't go, Jimmie Ward, last year's first-round draft pick, should again be the nickel back, though he, too, has been slowed by injury this preseason.

"But yeah, T-Brock ... we feel like everything is going to be great there," Tomsula said.

"We'll find out where T-Brock is at and I expect him to be absolutely fine."