Luke Shaw had suffered a recurrence of a long-standing groin injury and was playing through the pain barrier when he made the mistake which enabled Watford to score their crucial second goal in Manchester United’s 3-1 defeat at Vicarage Road yesterday.

Mourinho misery as Zuniga sinks United José Mourinho was scathing about Shaw’s error afterwards, singling the left back out for criticism for failing to close down Nordin Amrabat in the build-up to Juan Camilo Zúñiga’s 83rd-minute strike, but The Times has learnt that he was playing with a restricted physical capacity.

Shaw was substituted two minutes later by Mourinho, who did not disclose the player’s injury in his post-match media interviews. Instead the Portuguese condemned Shaw for failing to learn lessons from United’s 2-1 defeat by Manchester City the previous week, when Aleksandar Kolarov was given space to create Kevin De Bruyne’s opening goal, as well as questioning his “tactical and mental” attitude.

Mourinho exchanged words with Shaw when he substituted him late in the game CHIEF SPORTS PHOTOGRAPHER MARC ASPLAND Mourinho exchanged strong words with Shaw when he returned to the substitutes’ bench and went on to criticise his failure to “jump and press” Amrabat in several interviews, but he may have been physically unable to get closer to the Dutch winger. The 21-year-old aggravated a groin injury that has troubled him throughout his career earlier in the second half, but opted to play on rather than seek treatment.

Shaw’s injury is being assessed by United’s medical team today, with many of his team-mates shocked by Mourinho’s treatment of a player who has suffered with physical and mental frailties throughout his short career.

The former Southampton defender’s time at Old Trafford has been dogged by injury, including five hamstring and groin-related problems in his first season at the club before he suffered a broken leg at the start of last season, while he has had regular sessions with a sports psychologist after admitting to struggling with the pressure of playing for United.

Shaw’s relationship with Mourinho is also potentially problematic after the manager opted against signing him for Chelsea two years ago. Chelsea had been the favourites to recruit Shaw from Southampton before United eventually signed him for £28 million, but Mourinho advised the club against the move before revealing publicly that he did not think he was worth the money.