Arsene Wenger bemoaned Arsenal's finishing after watching his side waste numerous chances as they were held to a draw by 10-man Atletico Madrid in the Europa League.
The Gunners dominated the first leg of their last-four clash following Sime Vrsaljko's 10th-minute red card, Alexandre Lacazette heading in the opener on the hour mark.
But, with Wenger dreaming of the perfect end to his Arsenal tenure, a defensive slip allowed Antoine Griezmann to equalise and leave the tie finely poised at 1-1 heading into the return leg in Madrid next week.
After announcing he will step down as Arsenal boss at the end of the campaign, this was Wenger's final European home game at the helm.
Yet, after a combination of profligate finishing and a fine performance from highly-rated Slovenian goalkeeper Jan Oblak, Wenger was left ruing another game where missed chances could ultimately prove costly.
"We produced a performance we wanted to produce, but the result is not in line with the performance," he said.
"We can only look at ourselves on tonight's result because 1-0 is a perfect result at home. It was down to us after that not to make a mistake.
"We had 20 shots on goal, we have seen that against Manchester United (earlier in the season), where we had 33 shots on goal and lost the game. It's a story we've seen before.
"That's where the regret is. We were not clinical enough and unfortunately we gave a goal away which puts us in a very difficult position."
Atletico boss Diego Simeone watched much of the game from the directors' box after he fumed on the touchline in the early stages.
The Argentinian spoke after the match and expressed his excitement of what promises to be an intriguing second leg next week.
"It's tough to know what to say," he said.
"The ref decided to send off Vrsaljko and I thought an Arsenal player should have got a booking. When I protested he sent me off.
"They stood firm, after a long season, for 80 minutes in tremendous way. I have goosebumps thinking about the next match."