Walter Thurmond is an excellent talent that can't escape injuries. It's an old story. Many times, the injuries continue and the player is dinged up and worn down until his talent no longer merits the frustration. Sometimes, the injuries subside and the daring team lands a great talent and exceptional value.
Picks like Thurmond are thought risky, but I doubt Thurmond is much less likely to recover than an average fourth round pick is to develop. Apart from injury, and it was significant, tearing his ACL, MCL and PCL, Thurmond has no major weaknesses. He has pro level athleticism and speed, is good at most corner skills, a willing tackler and a hell of a ballhawk. So, equal downside, but excellent upside.