Manchester United manager Jose Mourinho said Marcus Rashford had played "fantastically well" after the striker gave Chelsea's defence a torrid time in a 2-0 win at Old Trafford.
Mourinho left top scorer Zlatan Ibrahimovic on the bench after Thursday's 1-1 Europa League draw at Anderlecht, with the Swede having complained of tiredness.
Replacement Rashford made the breakthrough as United threw the title race open, and kept their own top-four hopes alive, with Ander Herrera adding the second goal.
And Mourinho told Sky Sports: "Marcus Rashford played fantastically well.
"He had a very good game at Stamford Bridge in the FA Cup, exactly the same chance to score, because he is faster than their defenders.
"Today he scored and it gave the team more confidence, more stability."
Mourinho added: "Maybe we didn't 'rest' players ahead of Thursday [the Europa League second leg], we just chose the team we thought was the best team.
"We went to Stamford Bridge in the cup with same tactics, the game was totally controlled with 11 players, only the decision that made us play with 10 men for the second half and 10 minutes in the first half gave Chelsea a chance to be dominant.
"We knew that playing this way would be very difficult for them."
United's performance was one of their best since Mourinho took charge last summer and the Portuguese praised his team's attitude.
He said: "I think we have had very good performances -- Arsenal here, Tottenham here, when we played really well.
"But today I think was a special performance because it's also a special opponent -- the leaders, the way they play.
"I think we played really well, a very solid performance. We gave them double problems. We gave them problems when they had the ball because we controlled very well and we gave them problems when we recovered the ball because we were really sharp and fast and aggressive in our transitions.
"So, I am very happy with the performance. Very happy.''
The former Chelsea manager added to the BBC: "I'm happy -- not because it's Chelsea, it's because we need these three points.
"I don't feel extra joy at beating Chelsea. Nobody can doubt our credit to win the game."
United have not lost in the league since October, but remain outside the top four.
Mourinho said: "Normally you win the title if you are 22 matches unbeaten and we are struggling to finish top four.
"Why? Everybody knows why because we lost too many points at home.
"But it's a great feeling to know that it's difficult for us to lose a match, people fight until the end.''
Rashford added: "Everyone is together and we grafted to put the work in to get the result.
"It was a clever pass from Herrera [for the opening goal] -- we made eye contact and he put the ball exactly where I wanted it."
Press Association contributed to this report.