Arsenal boss Arsene Wenger has demanded improvement from his players after the 2-1 defeat to Hull ruined his 12th anniversary at the club.
Daniel Cousin's winner denied Wenger a return to the top of the Barclays Premier League table and ended Arsenal's unbeaten run at the Emirates Stadium, which had stretched back 17 months.
"We had the chances to win the game," said Frenchman Wenger. "The commitment was on the high side but we weren't completely switched on to the level you need to be to win the game. It was a good lesson for us. We now know that if our attitude isn't right, we can lose games."
The hosts had led through Paul McShane's own goal before Geovanni found the top corner from 30 yards, then Cousin added the decider as Arsenal wasted their possession and opportunities, a criticism they have faced after going without a trophy since 2005.
He added: "Human beings are not machines. Perhaps subconsciously we thought we would make it. After we went 1-0 up, we were a bit careless in not pushing on to score the second goal.
"We don't know how costly it could be but they were committed. It was a bit similar to (Arsenal's match at) Fulham. You can never afford defeats.
"We had a good chance to go top of the league but at the end of the day, if we had had the same level of concentration as Hull we would have won the game."
Emmanuel Adebayor had an effort ruled out in the first half for pushing McShane and Michael Turner - but Hull goalkeeper Boaz Myhill went untested for 45 minutes.
McShane bundled through his own net after Theo Walcott raided down the right just after the break, then Geovanni's rocket levelled.
Wenger was angry with the marking for Cousin's winner, and it was not the way he wanted to remember his 12th anniversary, adding: "There's nothing to celebrate, even if we had won."