Louis van Gaal praised his first half substitutes Chris Smalling and Ander Herrera for their display in United's 3-1 win over the Clarets at Old Trafford on Wednesday night.
The England international Smalling, who came on for the injured Phil Jones after five minutes, found the back of the net within 22 seconds of getting into the game. Burnley cancelled out Smalling's opener when Danny Ings headed home for the away team.
And, on the brink of half-time, Smalling’s header made it 2-1 after Angel di Maria's cross found Smalling, as the defender ended the clash chasing a hat-trick.
Herrera, who replaced Daley Blind also had a good game, as the Spanish midfielder battled hard and helped improve United's display in central midfield.
Despite the win the Manchester United manager wasn’t happy with his team’s all-round performance, particularly in the first half in which Burnley were the better side, and when asked if the early replacement of Phil Jones and Daley Blind upset his team, Louis van Gaal told MUTV: "I don't think the subs did badly! I like Smalling. He scores two times and he's never scored twice in a match because I asked him.
"Furthermore, in the second half, he was improving his game. I was very happy with him. Also Herrera, who was coming in for Blind, played very well, I think."
"It was not good in the first half," admitted van Gaal. "We didn't perform well and Burnley were the better team on the pitch. But we were ahead in the result and I was very happy with that.
"Okay, it is also from corner kicks. We train a lot on corner kicks but it was a lucky result at half time. I have to say we improved in the second half and created more chances, also scoring a third goal. We could have scored more and we only gave one chance away to Burnley."