SANTA CLARA –- Cornerback Kenneth Acker is coming off a season in which he started 13 games.
At 24, his best football should be ahead of him.
But Acker is in a battle to merely win a roster spot with the 49ers due to a 90-man roster loaded with seven recent draft picks at his position.
"He's doing a good job for us at corner and we're also cross-training him at safety," 49ers defensive coordinator Jim O'Neil said Thursday. "He's had a great attitude every day. I'm not down on him at all. He's competing, and he's competing for a spot on this team. He knows that."
Acker is the only primary starter from last season who appears to be down the depth chart. Tramaine Brock and Jimmie Ward have been working with the first team. Keith Reaser and Dontae Johnson, as well as rookies Will Redmond and Rashard Robinson have also gotten a lot of work ahead of Acker.
Acker, coming off a three-interception season last year as a first-time starter, is mixing in at safety, as well as getting some action on punt returns.
"We look for versatility," O'Neil said. "You only get so many up on game day. If you have multiple injuries at a position you need some guys who can go help out. He's not the only one. We're cross-training Dontae Johnson and Chris Davis. We have a lot of guys were playing corner (and) safety for us."