Arsenal manager Arsene Wenger says Everton's physical approach managed to disturb the Gunners as they fell to their first away loss of the season at Goodison Park on Tuesday.
Ashley Williams headed in a later winner as Everton's 2-1 victory ended a 14-game unbeaten run for Arsenal in the Premier League, even though they had gone ahead from Alexis Sanchez's free kick in the first half.
That goal seemed to wake Everton up, and Ronald Koeman's side managed to disrupt Arsenal's normally flowing attacking game after stepping up their aggression.
"It was a very physical game, we faced many challenges and we lost as well some balls that we are not used to, and I think it disturbed our game," Wenger told BT Sport. "And at the end of the day I must say we were a bit unlucky to lose as well."
Alex Iwobi had a shot cleared off the line in a frantic final minute of the game, while the Gunners were left to rue a big miss by Mesut Ozil shortly after the break with the score level at 1-1. Sanchez picked out Ozil in the box but the German could only fire over the bar.
"We had the first chances in the second half, especially through Mesut. After that they defended very well," Wenger said. "You have to give them credit, they played a cup game. For us [the key] was to not give them anything on set pieces and crosses and at the end of the day it was two defenders in their team who scored."
It was Arsenal's first league loss since the opening day of the season, and Everton's first win since October.
The result means the Gunners missed the chance to go top of the table, and gives Manchester City the opportunity to close to within one point ahead of their meeting on Sunday. City host Watford on Wednesday before welcoming Arsenal to the Etihad Stadium in a key clash between the title rivals.
Coleman levelled for Everton by heading in a cross just before the break after a period of pressure from the hosts.
Arsenal had controlled the first 20 minutes of the game, but Wenger said Sanchez's opening goal served as a catalyst for Everton.
"They were in a position where they had nothing to lose anymore," he said. "They played a little bit scared at the start. After that they had nothing to lose and they made the game very physical and then we lost our flow.
"I think in the second half we came back in it without creating as much as we are used to. But we did fight, I cannot fault our fighting spirit tonight. We know we lost some balls we should not lose, but maybe that's down as well to the intensity of the game."