Arsene Wenger praised Arsenal's character in the north London derby but felt Francis Coquelin's dismissal might have denied the Gunners a crucial Premier League victory over Tottenham.
Alexis Sanchez struck 15 minutes from time to salvage a 2-2 draw for the 10-man visitors at White Hart Lane on Saturday, after Toby Alderweireld and Harry Kane overturned Aaron Ramsey's first-half opener with two goals in the space of three minutes.
Arsenal, who came into the match following back-to-back defeats against Manchester United and Swansea City, were 1-0 up and containing Tottenham with relative comfort when Coquelin rashly dived in on Kane having already been booked.
Wenger's side remain three points behind second-placed Spurs and, after a result that is sure to please leaders Leicester City, the manager confessed to feeling conflicted over the outcome.
"I'm proud of the spirit the players have shown and the response, from 2-1 down with 10 men away from home we managed to come back with a point at least," Wenger told BT Sport.
"But we have big regrets because it looked like we were completely in control when we were cut down to 10 men. That's a regret of the game. Overall it's difficult to take."
Wenger was irritated to see Eric Dier escape a second yellow card when he pulled back substitute Olivier Giroud with the score 2-2.
"I warned [Coquelin] at half-time because he had a yellow already but I think that Dier deserved a second yellow as well. That could have changed the game."
Arsenal's stomach for an unpredictable title fight was questioned over the past week after some disappointing performances.
Wenger believes such scrutiny was justified but never doubted his players' battling qualities.
"Personally I never questioned the character of this team but when you don't win the games you have to accept that [criticism]. Respond on the pitch, that's all you can do.
"I think we did that today in a very convincing way."