The visitors, despite their numerical advantage, couldn’t break down Slaven Bilic’s side in the first half, and Mourinho responded by introducing Mata and Rashford early in the second half.
Their impact was immediate, with Rashford rounding off a sensational run with a pin-point assist for Mata after 63 minutes.
Mourinho, speaking after the game, conceded that his side didn’t play well against West Ham but secured the three points due to the impact of his second half substitutes.
“We didn’t play well. Mata and Rashford won the game for us,” he said.
“It’s job done, but congratulations to everyone on the pitch because I thought it was very hard. I was disappointed by some mistakes and decisions on the pitch, but that is fatigue, there are no miracles.
“We kept a clean sheet because David de Gea made a good save from Antonio, we had to move the ball and create space.”
Playing the majority of a game against ten men is not always a cakewalk. Slaven Bilic’s men immediately put bodies behind the ball after Sofiane Feghouli was controversially sent off after 15 minutes, giving rise to something not too different from any game at home last season: shifting the ball around with quiet intent whilst lacking end product, the opposition remaining compact, leading to a kind of uncomfortable deadlock.
Mourinho clearly knew this and didn’t take long to respond. On came Mata at half time to provide more craft and precision; then there was Rashford, putting the nail on West Ham’s coffin with raw, unbridled aggression on the left hand side.