Arsenal's Premier League title destiny was wrenched out of their own hands as they lost 2-0 at home to Aston Villa on Sunday but manager Mikel Arteta said how they react will be crucial.
A first loss in 12 league games brought back horrible memories of last season when Arsenal collapsed under the relentless pressure of Manchester City.
Late goals by Leon Bailey and Ollie Watkins secured a superb win for Villa on a day in which Manchester City were left as clear favourites to win a fourth successive title.
City, who thrashed Luton Town on Saturday, have 73 points from 32 games with Arsenal and Liverpool, who were stunned by Crystal Palace earlier on Sunday, on 71.
"That's the reality now," Arteta said when asked if Manchester City were now in charge of the title race.
"It's been the same for a few months. We knew this moment could come and now it's about reacting well. If one result is going to (derail us) then we are not strong enough.
"We had a great performance in the first half, it should have been three or four. Second half the momentum shifted. Now the moment is to stand up and be counted."
NO TIME FOR A HANGOVER
Thousands of fans streamed out of The Emirates after Villa's second goal as Arsenal's hopes of a first title in 20 years were dealt a mighty dent.
They still have six games left, however, and midfielder Declan Rice said all was not lost.
"Sometimes you need a game like this to re-set and re-focus and I still believe there will be loads of twists and turns," Rice, who was not at his influential best, told Sky Sports.
Arsenal can ill afford any sort of hangover after their first league defeat since New Year's Eve.
They face Bayern Munich in the second leg of their Champions League semifinal on Wednesday, having drawn 2-2 in the first leg.
They then go to Wolverhampton Wanderers next weekend when they would have the opportunity to go top of the table again, albeit having played a game more than Pep Guardiola's City.
"After losing any game they are frustrated and sad," Arteta told reporters.
"We have a beautiful opportunity that hasn't happened in 14 years to go to the semifinals of the Champions League. It couldn't come in a better moment.