Andre Villas-Boas swerved talk about his future at Chelsea after his side slumped to their third home defeat in the Premier League.
Aston Villa triumphed 3-1 at Stamford Bridge thanks to goals from Stephen Ireland, Stiliyan Petrov and Darren Bent, and Arsenal's win over QPR meant Chelsea slipped out of the top four.
Villas-Boas has reportedly been assured his job as manager is safe should he fail to win the title but the Blues are now in danger of not qualifying for the Champions League, something that could test billionaire owner Roman Abramovich's patience to the limit.
Chelsea's defensive problems were evident and they failed to add to Didier Drogba's first half penalty. Quizzed on what defeat might mean for his job security, Villas-Boas said: "You'll have to ask that question to the owner, but I have no other information on the contract.''
Pressed further on whether a top four finish was a minimum requirement, he replied: "I think the minimum requirement for a club like this is first place.''
He added ahead of Monday's game at Wolves: "Now we are fifth, below the top four. But we have to wait and see. It can change within 48 hours, though. That's a good thing. We have a chance to produce something.''
There were jeers from some home fans at the final whistle, which Villas-Boas admitted was justified. The Portuguese dismissed the prospect of closing the 11-point gap to leaders Manchester City - who play their game in hand at Sunderland on Sunday - as "fantasy''.
He added: "Our reality is a fourth-placed finish, but that is not good enough. We have to continue to pursue the best possible finish in the league, and a humble finish for this club.''
Villas-Boas then launched an unprompted attack on the festive fixture list, which gave his side four matches in an 11-day period, in contrast to United, whose games were spread over 15 days. "I don't think it's fair for the calendar to be spread in this way,'' Villas-Boas said, less than two weeks after insisting he had no problem with the scheduling.
"For us to go through this period with 48 hours in between, it should be done for every club. I know that television demands are high, but for all the players, they'll go through physical strain and physical integrity, which can undermine their careers or their Euro 2012 ambitions - and the club's objectives.''
Villas-Boas once again refused to accept any criticism of his defence, which conceded late goals to lose a home match for the third time this season. Rejecting suggestions the signing of Gary Cahill was now a matter of urgency, he said: "I don't see that performance being only related to defensive problems.
"If there is something to correct, we need to regain that confidence in the way we build up from the back. It's an easy thing to solve with players of this technical ability. I will keep away from defensive fragilities.''
Villas-Boas was also non-committal on whether Didier Drogba would still be at Chelsea at the end of the January transfer window. he striker scored his 150th goal for the Blues from the penalty spot to draw level with Peter Osgood and Roy Bentley in the club's all-time list.