There are about 6 options to play up front: Pacheco, Morgan, Yessil - All strikers by nature, won't get the chance because they've hardly had a chance in cup games so the league is out of the question.
Shelvey - Played against Young Boys up front, scored a goal and think he set the other one up (not too sure), would play this role well against West Ham I think
Gerrard - our best finisher out of the regular starting 11 and subs, might have lost a bit of pace but I'd trust him over anyone else in a 1on1 situation.
Sterling - think he should stay on the wing where he can get at players, don't think he would be good in the middle where his pace won't have as much of an effect.
I would choose to play Morgan there but it's a massive responsibility and may put too much pressure on the lad, remember what happened to N'Gog when Torres got injured. Shelvey is the next best option in my opinion.