Bruno Fernandes hailed Amad Diallo as "unstoppable" after the winger scored a 90th-minute winner in Manchester United's dramatic 2-1 victory at Manchester City on Sunday.
City defender Josko Gvardiol opened the scoring with a first-half header but Fernandes levelled from the penalty spot in the 88th minute and Diallo struck two minutes later.
Diallo, 22, has been the standout player for United since new manager Ruben Amorim arrived at Old Trafford last month and he delivered in dramatic fashion at the Etihad.
"I think there's still a lot to come from him because we really believe in his qualities, we know what he's capable of doing," United captain Fernandes told Sky Sports.
"He showed it today again. He's always happy, he's always alive, and this is why he gets the penalty, this is why he gets his goal."
He added: "We need him at this level, because when he's like this, he's unstoppable."
Diallo, named man of the match, said: "We wanted to win the game. We know it was not easy, obviously in the first half it was difficult, but in the second half I think we pressed good and we wanted to win.
"This is the derby, if you play this game you have to win, and we showed today we can win every game."
Fernandes said the United players were still getting used to Amorim's methods.
"It's a process," he said. "We know what he demands, what he wants from us. We've been speaking always before games that it doesn't matter what happens in the game, we stick to what we have to do, what we've been training to do – new routines, difficult, different positions."