Sir Alex Ferguson says Manchester United will not lose their nerve in the Premiership title race.
Ferguson described Chelsea's win as a "bit of luck"
United had their lead cut to two points after they suffered a shock defeat by West Ham and second-placed Chelsea scored two late goals to beat Everton.
"The result was nothing to do with nerve," said the United boss. "These things happen. We just have to gather ourselves and start another charge.
"We are still two points clear. The title is not decided in December."
However, he added: "It's not been a great day in the sense that Chelsea have come from behind, which is a bit of luck for them.
"But I'm not sure they are on a charge.
We've got something to build on
West Ham boss Alan Curbishley
"It was a result they have clawed out of nothing, but we have got to show our resolve as well. That is the hallmark of champions. We have proved that many times in the past."
United created several chances to win the game at Upton Park but were stunned by a Nigel Reo-Coker tap-in 15 minutes from time.
The weekend's other results mean West Ham are still in the relegation zone but new boss Alan Curbishley says the win will lift spirits after three successive defeats without scoring a goal.
"After Saturday's results we were desperate. We set off with a lot of enthusiasm and one or two of them were getting really tired," he said.
"It was a tough second half but the goal gave us that little bit of a lift.
"There has been a lot of criticism of the players and they have got to answer that and face the music.
"We had the first training session on Friday and they responded. Now we've got something to build on."