The Hammers went down to an early Robin van Persie strike but restricted the Premier League leaders and came close to snatching a point with Carlton Cole and Modibo Maiga going close.
December's fixture list is a little daunting with Chelsea, Liverpool, West Brom, Everton and Arsenal awaiting and comes on the back of the team suffering back-to-back losses for the first time this season.
But Demel told the club's official website: "If we play like that against Chelsea and are more clever in front of goal, we have a chance to win the game.
"Chelsea are a similar team to Manchester United, but they were worried last night. You couldn't hear their fans. At home this weekend I think we will push forward more.
"We don't need to hide because we have an opportunity to win the game."
With half a dozen players missing the trip to Old Trafford, manager Sam Allardyce was forced to call up members of his academy to the bench, including three who had just one substitutes appearance between them.
"We have been stretched for a while," said Allardyce. "My players ran their hearts out to stay in the game and we did put fresh legs on but after those we used, we are into the kids.
"At least Mark Noble is back for Saturday, which is important because we are tired."