He played like ass. He wasn't double bracketed at all in this game, from what I can tell. He also didn't seem to demand the attention of the Dolphins' coaching staff as far as putting their best cover corner on him goes. He was pretty much invisible. Hopefully this doesn't keep up and he earns what the team is paying him. But, if he continues to play like that and struggles to get open fast enough for Brady, he needs to be let go at the end of the year (maybe we can sign Welker).
That said, I'm not going to make a final judgement on him for the season just yet. The game plan wasn't exactly a masterful work of art. They had Amendola and Edelman running a lot of deep routes such as go routes and skinny posts while Brady was under a ton of pressure. The offense as a whole scored zero points in the second half, so it's probably not the best game to judge anybody on outside of McDaniels.