Mikel Arteta acknowledged Arsenal's 2-1 defeat at Tottenham dealt their European ambitions a "massive blow" but credited Jose Mourinho with making their lives difficult.
Arsenal took a 16th-minute lead through a thunderous Alexandre Lacazette effort in the north London derby at Tottenham Hotspur Stadium, but Son Heung-min pounced on Sead Kolasinac's wayward pass to David Luiz to equalise three minutes later.
The Gunners were on top in the second half but struggled to break down a Spurs side defending in two solid banks, with Toby Alderweireld snatching a winner for Mourinho's men nine minutes from time.
Arsenal consequently sit ninth with three games remaining, four points adrift of seventh-placed Sheffield United in the final European qualification spot – though eighth will offer a route into Europe if Manchester City's two-season ban from continental competition is not wiped out on Monday.
"Points-wise it's a massive blow because we know the results this weekend, but we'll keep trying while we have hope," said Arteta.
"We'll fight in the league and the FA Cup to do our best and try to finish as strong as possible."
He added: "I'm disappointed and frustrated. I'm really sorry for the boys first, because of the personality they showed to come here and show who we are.
"Nullify the opponent, press them high, just force them to kick the ball long and defend [in] a low block, which is exactly what we wanted to do, but if you give two goals away against these players it's difficult to win a derby.
"We can do more and be more incisive and exploit spaces better than what we've done. Sometimes the rhythm, the urgency and the link of distances wasn't exactly there, many times it was, and the purpose was there.
"To attack a template that is like this [puts one hand in front of the other] all the time is not an easy thing to do. We tried and had enough chances to win a derby.
"I can see what [Mourinho's] trying to do and, look, he wins again. It's two completely different styles. He manages really well, he has a good team behind him. He always finds a way to win it."
Arteta rued Arsenal's inability to cut out sloppy mistakes, which have proved so costly during his tenure.
"It is mentally tough, because in your mindset, you're ahead and controlling the game and everything we talked about is happening, and then you just give the moment away and mentally it affects the whole mood and momentum and our energy," said Arteta.
"We came back in the second half, we were even better, we were even more dominant, we were looking to score the second goal and then just in one isolated action we conceded the set-piece.
"We have to learn. Every game something happens, a little margin here and a little margin there. I'm sure we'll get there and I'm proud because I've never seen the play like the way they've played in this ground."