Sir Alex Ferguson had no complaints as Manchester United lost 2-1 at West Ham United.
Cristiano Ronaldo headed the champions in front at Upton Park before the Portuguese winger drilled a penalty wide midway through the second half.
West Ham then levelled through Anton Ferdinand before snatching a deserved win through Matthew Upson's header from Mark Noble's free-kick.
Ferguson praised the Hammers' performance as Alan Curbishley masterminded a third successive win over the Red Devils.
"We were beaten by a better team I think," Ferguson told Sky Sports. "I don't think we measured up to our normal performance.
"When that happens, particularly when the team is motivated against you, you are going to get a hard day, and we had a hard day.
"They are human beings and you can't expect them to be perfect all the time. We had a perfect performance in our last game at Sunderland and this was a disappointment today.
"I think we struggled today. They were very competitive and aggressive West Ham and they were always about us, tackling us everywhere.
"Getting the lead, and missing the penalty - that would have killed the game, but I couldn't see it happening. If you are losing goals from set-pieces, you know you're not at your best."
Ferguson is now looking for his table-toppers to respond in the New Year's Day fixture with Birmingham City at Old Trafford.
He added: "It's a great team I've got, but we just have to galvanise ourselves.
"A great reply if you always give a bad performance is to have a good one next time."