Yeah, I'm in the camp that Thurmond won't beat Winfield.
1) Winfield is one of the better slot defenders in the NFL. Winfield is better at coverage vs slot WRs than Trufant was presumably from his years of practice with Percy Harvin.
2) Winfield is one part nickel corner, one part nickel linebacker.
3) Forcing Thurmond to stay at 4, will reduce his re-upping cost after this season, that plus his injury history will allow us to retain him on the cheap and we can plug him at Nickel in 2014.
4) As others said, I wouldn't risk extensive playing time for an injury riddled player.
5) And as others said, Thurmond is likely only CB we have that can play in all spots consistently and effectively. Winfield doesn't have the speed to play outside, Sherman and Browner don't possess the quickness to play inside. Thurmond can do it all which makes him key backup to all spots.