You're right.
We haven't really excelled since early season and that's somewhat worrying. The goals have dried up significantly (although pre-signing Torres we banged in 8 in 2 games if I'm not mistaken?) and we're not playing like anything more than a 3rd/4th/5th placed team. I think it's gonna be more challenging than some will admit to come 4th, especially considering we've gotta play United twice.
That said, Spurs have been lucky of late, that's gotta run out soon especially when the CL resumes 'cause they're not particularly used to massive mid-week fixtures and then backing up in the PL at the weekend.
The top 8 as it stands:
Man Utd 26 57
Arsenal 26 53
Man City 27 49
Tottenham 26 47
Chelsea 25 44
Liverpool 27 39
Sunderland 27 37
Bolton 27 36
The four remaining games against Spurs, City and United (2) are of paramount importance, obviously.