The Chelsea boss was unusually quiet on the touchline and took responsibility for the defeat, as Marcus Rashford and Ander Herrera fired Jose Mourinho's men to a victory over the Premier League table-toppers.
But with United winning, Chelsea's lead has been cut to just 4 points, and we've now very much got a title race on our hands.
Mourinho said United's win showed that had Herrera not been sent off in last month's FA Cup defeat at Chelsea, it would be his side facing Tottenham in the semi-finals on Saturday.
While, Chelsea's lead at the start of April was 10 points, two defeats in four league matches has seen Spurs - who have won seven straight top-flight games - eat into that advantage.
"It won't be easy because I think Tottenham now is the best team and they are in good form and they have a lot of enthusiasm".
"I am concerned, we have to work together and find quickly the right desire and ambition to win this title". He was downcast but remained calm and his players will surely appreciate and respect his willingness to take sole responsibility by moving front and centre to shield them from the measured criticism that would have been deserved after this rare lapse.
Chelsea face some seemingly manageable assignments against Sunderland and Middlesbrough in the run-in to the finish line, but they also have a tricky prospect against Everton to deal with in that mix as well.More news: Jackie Robinson broke Major League Baseball color barrier 70 years ago today
"The pressure is normal", he added.
"We were tactically very good and the players did an incredible job", Mourinho, who pointed to the United badge as he walked off the pitch, told Sky Sports. "I am very happy", he said after the victory at Old Trafford.
He said: "No, the satisfaction is for different reasons". We need to realise it is not over, we need to realise there are points to play for, and we have to dig in.
Ibrahimovic has already made 44 appearances and scored 28 goals as United reached the latter stages of three cup competitions and challenged for a place in the Premier League's top four.
"Alonso had a virus during the night and we tried with the doctor to recover him for the game but it wasn't possible".
"We couldn't let the defenders bring the ball out and play and we knew if we did that then the players behind us, the midfield and defence, would do their job of marking the players behind us".