Manchester United recovered after being rescued by the heroics of goalkeeper David de Gea to run out comfortable winners at Brentford.
Ralf Rangnick's side survived a torrid opening 45 minutes, when their performance was laced heavily with mediocrity - as De Gea made key saves from Mathias Jensen and the home side missed other big chances.
It was a different story after the break as United, no doubt fired up by a few well-chosen words from Rangnick, turned up the intensity and the quality to punish Brentford for their profligacy.
Teenager Anthony Elanga headed his first goal of the season from Fred's pass 10 minutes after the break before Cristiano Ronaldo's superb chest pass helped Bruno Fernandes set up the second unselfishly for Mason Greenwood.
Ronaldo produced a ridiculous show of petulance with a slow stroll off, some very obvious muttering and a burst of anger on the bench after he was substituted with 20 minutes left.
But Rangnick's change was fully justified as substitute Marcus Rashford scored with a smooth near-post finish after 77 minutes, with Fernandes the creator again.
Ivan Toney pulled one back in a scramble late on but the damage was done for Brentford when they failed to cash in after carving United open in the first half.