Hiddink said Chelsea should focus on the UEFA Champions League, where it faces Barcelona in the semifinals, and the FA Cup final against Everton on May 30.
"We said before the game that the two teams chasing Man United must not waste any points to keep in the race," Hiddink said. "The facts are we lost two points. We must be realistic. Maybe mathematically there is still a chance but on the other hand you cannot waste points. Now it is difficult. We have to focus now on only two roads, in the Champions League and later against Everton in the FA Cup."
Howard pushed away a shot by John Terry and made a finger-tip stop to push over Salomon Kalou's drive. Chelsea's best chance, though, came in stoppage time when Didier Drogba hit the crossbar.
Everton is in sixth place, one point behind Aston Villa.
"It means a lot to me to finish fifth," Everton manager David Moyes said. "We've had three out of four top six finishes in the last four years and if we do it this year it will be four out of five. It is a sign that Everton are becoming a side that can compete at a top level. Maybe not quite with the top boys but with what we've got it's a decent effort."
In United's win on Wednesday, Gary Neville and John O'Shea both were injured -- Neville going off after 13 minutes after a clash with Nadir Belhadj and O'Shea, who replaced him, went off after 52 minutes -- and will miss Saturday's home match against Tottenham.
United leads second-place Liverpool by three points and also has a game in hand on the Reds.