49ers sort out crowded defensive backfield

With nine 49ers cornerbacks eyeing fresh vacancies in the San Francisco defensive backfield, secondary coach Tim Lewis hasn’t refrained from shuffling new faces in with veterans to better assess his unit.

Sixth-year cornerback Chris Cook said:

“We come in every day and it’s a different depth chart. … I think he (Lewis) is just playing it by who he needs to see more of. To see what guys can do against certain looks he has to get them out there.”

Free agency departures of 2014 starters Chris Culliver and Perrish Cox left openings in a secondary already hampered by injuries.

Cook, 2013 starter Tramaine Brock, and 2014 first-round draft pick Jimmy Ward all missed time due to injuries last season. Still, they hold an advantage in the pursuit of playing time, said 49ers 2014 fifth-round draft pick Keith Reaser, who spent last year rehabilitating an ACL injury sustained during his senior season at Florida Atlantic:

“Some of the veterans have a little bit of a jump on us. … But I think it’s going to be a really good competition at camp. We’ve all been rotating, maybe one day I’ll be at two’s with the corners and then the next day I’ll be at one’s with the nickel.”

Veteran free agent Shareece Wright and 2014 fill-in Dontae Johnson round out the crop of cornerbacks who earned significant playing time last year, with Reaser, Kenneth Acker, Leon McFadden, Marcus Cromartie and rookie Mylan Hicks also in the mix.

The loss of consistent personnel has stressed the secondary as a whole, though the competition for the newly-empty spots has fostered a high level of play, said reigning 49ers team MVP and defensive backfield captain Antoine Bethea:

“P-Cox and Cully had good years for us last year, but we most definitely have some guys that are going to step up for us this year. … Competition is always good and when training camp gets here it’s going to be even better. There’s a lot of guys of out there making the correct plays and going hard.”

Sophomore corners Reaser and Acker are joining the veterans in returning from injury, and have impressed head coach Jim Tomsula with their mental progress despite missed rookie seasons:

“They’re moving around pretty good. … It’s not new to them. The whole approach, the nerves that you see with a young guy coming in, there’s none of that.”

Acker echoed Tomsula’s confidence, adding that traveling and participating in activities with the team sped up his development when he wasn’t able to take snaps:

“A lot of it in the NFL is getting comfortable with who you are as a player and as a person. … I think the 49ers did a really good job with that, we didn’t feel left out in any way. We just knew our time would come.”