I really doubt Dustin Keller is "good to go." The guy totally shredded his knee. He'll probably take a route similar to Andrew Quarless. If he plays at all this season, I would be surprised. And even if he does play, I don't expect him to be particularly effective. He wasn't a whole lot more than an average tight end recently before a massive knee injury. He's not overly big either, at "only" 6'2. Jordy Nelson is taller.
If I were a general manager, I'd easily pass unless I thought I could sign him, place him on injured reserve, and see if he can contribute anything next season. All things considered, just doesn't seem worth it for a smaller average tight end that's going to be 30 this year. I'd rather his reps go to Brandon Bostic.