Well - we have already player Brighton and West Brom twice each, so they are out of the equation in that respect.
If Newcastle lose Calum Wilson to injury then we may have a chance of catching them. To be in a position of needing a win against them in the last game of the season to stay up - is probably the best we can hope for at this stage! The problem is we probably also need to beat Burnley twice (can't see that happening) and beat Sheffield United as well (we won't in our current form)!
Even accounting for 4 wins against the above - we will still need to win at least two or three games against other opposition, so I think that is the even bigger question mark:
West Ham (bogey team)
Crystal Palace (they concede a lot of goals but mainly against superior opposition - maybe we have a chance if they are without Zaha)
Leeds (they also concede a lot of goals and we gave them a game last time out)
Aston Villa (they have had a few bad defeats lately)
Wolves (probably the most winnable?)