Lukaku also had a goal scrapped for fractional offside in the 57th minute before Andros Townsend spurned a gilt-edged chance for Palace when he shot wide from 10 metres after a good solo run.
"But we were not enough ambitious or intensity to do it".
Jose Mourinho said before the game that he was confident his team would be in the Champions League places by the end of December but, after another frustrating afternoon, that is looking increasingly unlikely. I think we played very badly in all directions - physically, mentally, technically and tactically.
"N'Golo for us is not just an important player, he's a "determining" player", Sarri said.
"The best defensive-midfielder in the world - I'm sure he's got his new contract from what he's done previously - and listening to his manager say he could score more goals". We knew the spaces they were not giving, but we did not have enough ambition or intensity to do it.
There was one moment during the second half against Palace that left United fans - those inside the stadium, and those watching the match at home - with their heads in the hands.
Why Chelsea Need a Commanding Performance Against Spurs
Liverpool produced a superb second-half performance as they won 3-0 at Watford , having been frustrated in the first half. The Spurs star told BT Sport: "We knew it was going to be a hard game and we knew we had to start strongly".
Then, he moved on to join the London club and won the Premier League title two years ago under Antonio Conte.
"When we decide to make a rotation, we will make (one), when we need to. I'm disappointed with the performance".
The defender has not played since being taken off early in the 3-2 win over Newcastle on October 6 when United were 2-0 down.
"Anthony stayed with us, he didn't go to the national team, the national team was aware of his problems and with permission he stayed, he worked really hard on that", Mourinho said, referring to the French forward's muscle problems.
"There aren't many teams in our position who will come here and win, or get a point as we have done".