Manchester United manager Louis van Gaal heaped praise on Ghanaian defender Timothy Fosu-Mensah.
Fosu-Mensah, 18, started against Watford alongside Daley Blind in central defence after featuring as a substitute in the Arsenal win last weekend.
Watford had deadly duo Odion Ighalo and Troy Deeney in attack but the Manchester United youngster kept them quiet before Juan Mata hit a late winner.
"Timothy has saved us three times, I think, because of his speed," Van Gaal said.
"So I was very pleased that he was on the pitch. He wanted to be changed early in the second half [because he picked up a knock] but I let him stay on because he always closed the door for us."