SANTA CLARA -- Veteran cornerback Chris Cook has been making the most of his first-string opportunities to replace Carlos Rogers, even wearing the same No. 22 jersey in the 49ers' backfield.
Cook nearly intercepted a Colin Kaepernick pass in the end zone to finish Tuesday's practice.
"I'm doing everything I can to put myself in the position to be out there with the starters, whether it being in nickel or base," Cook said.
Cook is lining up at right cornerback while Tramaine Brock is on the left side. Potential starter Chris Culliver is being limited to individual drills while he returns from a 2013 knee injury. First-round draft pick Jimmie Ward is also being kept out of team activity while he recovers from March foot surgery.
Cook played his previous four seasons with the Minnesota Vikings before signing a one-year deal with the 49ers.
"I like this defense a lot and feel it fits my style of play," Cook said. "I like to man up, and a lot of things we do ends up being man coverage."
Coach Jim Harbaugh called Cook an ascending player, adding: "He's showing up and making plays. He's getting his hands on the ball, he's made interceptions and he's done a good job."
Cook credited his coaches with enhancing his development in the 49ers' scheme.
"The coaches here really take care of players, especially (secondary coach Ed) Donatell, who puts in a lot of extra time with me working on my craft, and I appreciate it a lot."