Arsenal boss Arsene Wenger said he was happy with his side's position at the top of the Premier League, despite having their lead cut to a point.
United have had nine home games and seven away, while we've played eight each so I'm happy we're top of the league
The Gunners' 2-1 loss at Middlesbrough ended a poor week for the Londoners, having started it six points clear of main title rivals Manchester United.
"We can't complain, we weren't sharp after four away games," said Wenger.
"I know the gap is only one point now but we would have taken the position we are in at the start of the season."
Wenger's side could lose their top spot next Sunday when the leading four sides play against each other.
Arsenal host Chelsea while Liverpool entertain Man Utd.
A Stewart Downing penalty and Tuncay Sanli strike rendered Tomas Rosicky's injury-time reply redundant as Boro shocked the Gunners at the Riverside on Sunday.
And Wenger conceded: "Boro were clearly sharper than us after a difficult period of games, which seem to have taken their toll.
"We have a few injuries at the moment, but it is easy to blame the players who are not here and I believe in the players who played today.
"This season will be a big, big fight for the title. United have had nine home games and seven away, while we've played eight each so I'm happy we're top of the league."
Middlesbrough boss Gareth Southgate, meanwhile, had no hesitation in labelling the victory Boro's best performance of the season.
"No question," he said. "We played very well here against Birmingham but the quality of Arsenal's team is there for all to see. Hopefully the players can see what they are capable of now.
"It's been quite depressing at times but we've tried to stay positive and one or two are starting to score goals now. But it's one afternoon and we have to be more consistent."
Hopefully the players can see what they are capable of now
Goalscorer Downing added: "It's a massive win, and even better that it's come against one of the top teams in the league.
"(Arsenal) let you play a lot so we moved the ball quite well. We seem to play well against the top teams. We need to get the consistency in our game and get up that league."
And striker Jeremie Aliadiere said: "I was very motivated and we needed those three points.
"It's a good start, we have picked up a few points in the last few games. We wanted to work really hard and get three points and this builds confidence for the team."