Either Buttner is LW or Rafael is RW. Either way, decent line-up.
I would assume they would push Rafael up with Smalling behind as I haven't seen Smalling ever play left back. It's a pretty good team and Smalling/Vidic will be good at dealing with the physicality of West Ham. Also, got some good options on the bench.
I just hope Rafael's RW slot doesn't distract him too much of his defensive duties when he does return to RB, especially if him playing RW becomes a regular thing. This season, he's absolutely nailed the balance between attack and defence.