London - Arsenal manager Arsene Wenger said Marcos Alonso's opening goal for Chelsea should have been ruled out after his side crashed to a 3-1 defeat at Stamford Bridge on Saturday.
Arsenal right-back Hector Bellerin had to go off after being caught in the face by Alonso's forearm as the wing-back leapt to put Chelsea in front in the 13th minute.
Eden Hazard, with a sublime solo goal, and Cesc Fabregas put the game to bed for Chelsea, who now have a 12-point lead over Arsenal at the top of the Premier League table.
"It was a foul. It was 100 percent a foul. It was even dangerous play," said Wenger, who watched the game from the stands as he served the third game of a four-match touchline ban.
"That doesn't take anything away from the performance of Chelsea."
Wenger revealed Bellerin had been left so dazed by Alonso's challenge he did not know his side were trailing as he left the pitch.
But when Chelsea manager Antonio Conte was asked if Alonso had fouled Bellerin, who was replaced by Gabriel, he replied: "In England, never. No."
Hazard doubled Chelsea's lead with a sublime solo goal in the 53rd minute, scything through the Arsenal defence from the centre circle before lifting a shot over his former team-mate Petr Cech.
"It is always good to score beautiful goals against a massive team," Hazard told Sky Sports.
"I enjoyed the game and the goals. We scored three beautiful goals and we deserve to win this game.
"We are still top of the league. We have good confidence and we want to finish the season and stay top."
Asked what he had been thinking as he bore down on goal, twice beating Laurent Koscielny and leaving Francis Coquelin in a crumpled heap, Hazard replied: "To dribble like I did.
"It is not like this in every game. I know I need to score more and today I did. I am happy."
Substitute Fabregas added Chelsea's third, lobbing in from 25 yards after Cech had shanked the ball straight to him, before Arsenal replacement Olivier Giroud notched a stoppage-time header.
"It was an important game," Conte said.
"I consider Arsenal one of the six teams that can fight for the title until the end of the season. To put them 12 points behind is very important for us."
Wenger conceded the title was now Chelsea's to lose.
"Chelsea are in a very strong position," he said. "They look solid, difficult to beat and we needed to be better today.
"They don't lose against the big teams and that is always the secret to win a championship."