I'd make just a few alterations to the team that started against Leicester, but I think that is all that is needed to make a distinct difference. For a starter, I would continue with the 4-4-2 diamond, as it is the most suitable system for our personnel, but it's probably not ideal for a tricky away fixture against a good opponent.
On the topic of our personnel, Rojo was hugely disappointing and constantly out of position at left back, but I think (hope) we will see a big contrast between his performance at full back and at centre back. He's far more adept at the latter, so I hope we see Rojo at centre back and Shaw at left back. Kind of enforced team selection either way!
The final change, would see Mata behind the front two displacing Rooney in that position and at the expense of van Persie's starting position. Accommodating all three of van Persie, Rooney and Falcao significantly hinders the team on the whole and unbalances the side. No more than two of those three should start at any time. Even if West Ham are a very physical and athletic side, I expect us to perform better with Mata and Rooney even if he does neglect the defensive side of things and struggles with physicality and intensity.
We are the home side and shouldn't cater to opposition like West Ham. The initiative and impetus should be with us and it's difficult to remedy the defensive situation when we have Carrick injured and Fletcher looking poorer and out of his depth with each passing game and a lot stems from the lack of leadership and organisation as a defensive unit.
XI:
de Gea
Rafael - Smalling - Rojo - Shaw
Blind
Herrera - di Maria
Mata
Falcao - Rooney
Subs: Lindegaard, Fletcher, Valencia, Pereira, Januzaj, van Persie, Wilson
I'm pretty sure we will concede given West Ham's form and attacking prowess and physicality, but I don't see a better alternative to that team considering our plethora of injuries.
4-2.