I think Whitner comes back for less money, he likes the team and our defensive system favors his style of play. Brown will walk, after Vontae Davis and Aqib Talib, he would be far and away the best free agent CB. If we are smart we sign Cox to a multi year deal, he was better than Eric Wright and he is a good depth corner, he's still fairly young and is experienced in our system. Plus we get Cully back. As far as the draft goes I would go after the best corner available in the 1st round and also I would consider getting a big physical corner like Keith McGill or Stanley Jean Baptiste.
I think Whitner comes back for a fair price, too. Even though he can cash out, he's said he likes being in San Francisco and playing for a contender. I think he feels like his time in Buffalo was wasted because he was playing meaningless games at the end of the year.
I think the Niners have an outside shot of resigning Brown, too. I believe I read somewhere that the contract that Brock took was essentially the same contract they offered Brown. He'll test FA, but he might come back on a 1 year deal or something. Even so, I think we still draft corners. Do we draft a corner in the 1st round? I don't know. The staff has shown a good eye for getting corners in the middle to late rounds of the draft, so maybe they have something higher on their list.
As far as Cox, he was descent. It'll be interesting to see if the Niners sign Cox or Wright. I know Baalke really pushed for Wright, but the coaching staff obviously trusted Cox down the stretch.
Also, if the Niners and Kap don't get a contract ironed out, I'd look for the Niners to draft a QB in the later rounds as an "insurance" policy.