I think that all depends if we beat Southampton or not. 15 days is a long time to stew after a defeat.
What about a draw?
Like the poster says above, its a lot of time to hopefully get Sakho back, and to work on a coherent defence.
If we DO LOSE to Southampton. Then the game that we watch Spurs play will be Chelsea vs Tottenham (and West Brom vs Man United)- if Tottenham lose that, we would remain 3/4/5/6 (that's the entire range I think) ahead of them, but we'd also have a game in hand. Quite a boost?
Lose to the Saints and it's possible they could only be 5 points behind us by time we play them. Albeit we will have a game in hand on them.
If you mean the Mancs, then no they can't - they miss a game when we play Southampton because of the Carling Cup Final. If we lose to Southampton and they beat West Brom (a week apart), they could be within 8.
They would have a game in hand on the rest of the league against Man City at home, yet we'd have one as well, against Sunderland.