Honestly, if we lose to Chelsea we might as well start thinking about it.
However, this can change very quickly over the next three PL fixtures or so. We play:
Chelsea (A)
Brugge (A)
Watford (H)
Brugge (H)
Everton (A)
Chelsea has 6 Points on us at the moment, 9 if they beat us on Monday. It's incredibly hard to see us overtaking them if they beat us. I'd be targeting 18-20 wins and a points total in the mid-60's if you want to have a chance to finish 4th this season. Chelsea would then have 13 wins, so only potentially need 5 from the remaining 12 fixtures. They could still fluff it, but us losing our only chance to take points off of them directly would be a huge blow and make me think it's almost over. But, they play Tottenham after us with Bayern in the Champion's League after that so it is a huge make-or-break month for them too. We really need to be beating Chelsea and Watford, hoping for a draw with Chelsea/Spurs and we're in a strong position just a point behind both Chelsea and Spurs by that stage. We also have big games against Spurs, Sheffield United and Man City coming up soon, so it's a key period. If we can come out of it within touching distance then we've every chance of fourth. If we're failing to beat all these teams around us (Chelsea, Everton, Spurs, Sheffield United) then we have to go for the Europa League.
My expectation is that if we lose to Chelsea and don't get maximum points from Watford/Everton we're not doing it anyway. However, if we did get past Club Brugge, the round of 16 isn't until March 12th. Sadly, we'd play the following fixtures then@
Man City (H)
EL Last 16
Spurs (A)
EL Last 16
Sheffield United (H)
So, it's another huge set of fixtures. If we didn't take maximum points from our remaining February games and that game on 1st March against Everton, I highly doubt we'd manage to stay in the race. We will probably lose to Man City at OT (seems to be the usual outcome lately) and then it's almost surely a must-win against Spurs in-between our EL game if we're in it. Of course, we have to progress in the EL first but we really should against Brugge. It's such a difficult decision whether to stick or twist, but I'm gonna go out on a limb and say if we don't get 7 Points from Chelsea, Watford and Everton then we should go for the Europa League. Putting in huge effort against Man City, Spurs, and Sheffield United around or Europa League Last 16 Fixtures would probably just mean we weaken our chances of everything at the same time. We'd probably end up out of the top four race and out of the Europa League (depending on who we drew of course).