Arsene Wenger was left "disgusted" by a controversial offside decision as Arsenal's Premier League title ambitions were held up by Sunderland.
The Gunners were looking to take full advantage of Manchester United's midweek defeat at Chelsea to eat into their four-point lead.
Arsenal - who head to Barcelona on Tuesday for the second leg of their Champions League last-16 clash - slowly gained the advantage after a bright start by the visitors, and Nicklas Bendtner's angled shot was tipped over by man of the match Simon Mignolet.
Samir Nasri was also denied by the agile Black Cats keeper after a fine 20-yard free-kick, while substitute Marouane Chamakh crashed a header against the bar in the second half.
However, Andrey Arshavin should have been given a penalty after being pushed by Titus Bramble as he shaped to shoot, and then had a goal incorrectly ruled out for offside by the assistant on the far side after bursting clear.
Wenger admitted it was the last thing his injury-hit and battle weary squad had needed following the shock Carling Cup final defeat to Birmingham at Wembley last weekend.
"I am too disgusted to speak about these things," the Arsenal manager told BBC Sport.
"What can you say? We put a lot of commitment into the game. I believe Arshavin was not offside, but what can you do?
"These kind of things have too big an impact on the Premier League and we are really disappointed but we have to take it on the chin for the next game, but we feel really justice has not been done today and it is not the first time."
When he gave his main post-match interview, the Gunners boss was in more reflective mood.
He said: "It is another disappointment.
"You do not want to have things going against you, but what can we do? Now we just have to focus on Tuesday night."
Wenger continued: "I am very happy with the performance, defensively we were very good and gave a lot physically, and I cannot fault the players' attitude.
"True, we lacked a bit of creativity and sharpness in final third, but had two decisions going against us today which punish us severely, especially the offside, which is not offside.
"To win this game 1-0 was important."
Wenger, though, was careful not to hit out at referee Anthony Taylor or his team any more, perhaps mindful of the Football Association action against United boss Sir Alex Ferguson.
"What can I do about it now?" he said.
"It is my job to deliver football games and the referee's job to give the right decisions.
"I can explain my job, but to [explain] the referee's decision? That is your job."
Wenger tried to see the positive side of this afternoon's disappointment.
"We have played 11 games, with eight wins and three draws, so we are quite consistent with our results," he said.
"Today's result comes at a bad moment.
"Will it psychologically have such a big impact on the championship? I don't think so."
Arsenal are already without Holland forward Robin van Persie and England winger Theo Walcott for their trip to Spain, but captain Cesc Fabregas has a chance to be in the squad.
Midfielder Jack Wilshere will be assessed over the weekend.
"He has an ankle problem, but we will see how he responds to treatment," Wenger said.
"He will be out of training maybe a day, then on Monday maybe back. We will see."
