Mikel Arteta challenged Arsenal to show they have the character to cope with a 3-2 defeat against Manchester United that breathed new life into the Premier League title race.
Arteta's side would have moved seven points clear at the top with a win at the Emirates Stadium on Sunday, but they squandered the chance to consolidate their title charge.
Lisandro Martinez's own goal put Arsenal ahead before Bryan Mbeumo equalised late in the first half.
Patrick Dorgu's superb long-range strike gave United the lead after the interval, only for Mikel Merino to scramble home an Arsenal equaliser in the closing stages.
Just minutes after Merino netted following a mistake by United goalkeeper Senne Lammens, Brazilian forward Matheus Cunha stunned the Gunners with a brilliant drive from 25 yards.
Instead of having a commanding lead in the title battle, Arsenal are now just four points clear of second-placed Manchester City and third-placed Aston Villa, who won 2-0 at Newcastle on Sunday.
-- NIGERIA ONLY --
"The margins are extremely small and we made them even smaller. Now we have to react and see what we are made of," Arteta said.
"Today we were not at our level and we paid the price. We just gave it away.
"We gave them a goal which is unusual and painful, then they had two brilliant moments with incredible goals. We were not at our best.
"In the first 30 minutes we were in total control, scoring a goal, but after that so many times we gave the ball away in important areas. We started to lose control and dominance and it became a chaotic game."
STILL IN CONTROL
It was Arsenal's first defeat in 13 games in all competitions since losing at Villa in December.
The Gunners lost at home for the first time in 18 matches in all competitions since a defeat against Bournemouth in May.
Arsenal still control their destiny, but goalless draws against Liverpool and Nottingham Forest had sparked concerns from their anxious fanbase, and this was another alarming result for Arteta.
Arteta has not lifted a trophy since the 2020 FA Cup and Arsenal, who have not won the title in 22 years, face a test of their nerve in the coming weeks after blowing significant leads at the top in previous title races.
"The players have given us so much joy and performances, they deserve to be reminded how good they are," he said.
"We have to learn from it. Defeats are part of winning and you have to take them and remind the players how good they are. When you draw or don't win and lose, that's when you have to show the togetherness and unity.
"To get where we want to be, defeats are part of that for us, as for any team."