José Mourinho was first out before kick-off as promised during Friday’s extraordinary extended monologue in which Manchester United’s manager promised to face his responsibilities. Really required, though, was safe passage to the FA Cup semi-finals, and this was duly secured.

Yet Mourinho’s team were tame again, this win coming thanks to goals from Romelu Lukaku and Nemanja Matic, the only two players named as consistently excellent during that 12-minute defence of his record. The Portuguese’s post-game assessment was frank. Mourinho stated he did not “like the game”, and questioned the courage of many of his players to don the United shirt.

José Mourinho launches attack on Manchester United players despite win Read more

Mourinho’s standout selection choice was the exclusion of Alexis Sánchez, the Chilean dropped for the first time since he signed in January and unused from the bench. Paul Pogba suffered the same fate: after failing to regain his place after being a substitute in Tuesday’s dire Champions League exit at the hands of Sevilla, the Frenchman also went unused.

In all Mourinho made five changes, as did Chris Hughton, who gave Brighton’s £14m record signing Jürgen Locadia a second start, with their top scorer Glenn Murray on the bench. Sergio Romero retained his place as Mourinho’s cup goalkeeper, and Luke Shaw, the left-back who had started in previous rounds, started again. Yet despite helping to create Lukaku’s 37th-minute opener, Shaw was removed at the break.

Cue more frankness from the manager. “Luke in the first half – every time they come in his corridor, the cross was coming and a dangerous situation was coming so I was not happy with his performance,” Mourinho said.

Nearly half an hour had passed before United threatened for the first time. The ball was exchanged between Anthony Martial and Juan Mata and, when Mata took aim, United won a corner. Mata took it, and after panic in front of Brighton’s goal Chris Smalling hit Tim Krul’s left post.

Lukaku’s opener came after Shaw danced down the left and pulled the ball back to the excellent Matic. The midfielder clipped over an instant cross and up rose the Belgian for a 30th of the season in all competitions.

This brought relief for Mourinho and his players and United did brighten for the rest of the half, though it was a relative improvement only. The truth was that when the break arrived it had not been the kind of play to suggest that the 2-1 defeat by Sevilla was a blip.

Instead, when the sides wandered off the sense was of a tie still in the balance, and United were lackadaisical again after the break. Shaw was replaced by Ashley Young with Mourinho’s words confirming this as the latest setback in his United career.

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After an opening that had Brighton trapped in and around their area, United’s flakiness showed once more. The ball was given to Pascal Gross and he had a yard of space to aim at Romero’s goal, the shot just missing to the keeper’s right. Gross then floated the ball on to Leonardo Ulloa’s chest and, when it came to Beram Kayal, he pulled the trigger to warn United that Brighton believed they could equalise.

They came agonisingly close through a moment of Locadia magic as the Dutchman fizzed a 20-yard shot at Romero’s top-right corner, the Argentinian flying high to save.

United’s best hope of any attack at speed was on the counter. When Matic strode away from his area and found Jesse Lingard, suddenly Brighton were scattered. Anthony Martial received the ball next, but, when he tried to find Lingard, the pass again went awry.

Now, there was another lull in quality from Mourinho’s team. Mata tried a ball over the top aimed at Martial but it was too long in what, otherwise, was a passage of Brighton possession. Hughton’s side seemed to be finishing better. First Matic blocked an attempt, then Smalling did the same to a Locadia shot.

This woke up United as Lukaku and later Mata had crosses blocked. The latter seemed a little unlucky to be replaced by Marcus Rashford. By the close Matic had headed in Young’s free-kick and United had done what was needed, yet it left Mourinho in full-throttle complaint mode.

“Sometimes there is a contradiction between what you work on in the past two days and what you did on the pitch,” he said. “That is more frustrating than the result. I blame everybody.”

Hughton said: “I am delighted with the performance. The only differences were the moments in front of goal and the quality they can produce. We were always in the game.”

This is what could hobble United’s aim to win a 13th FA Cup. They always allow the opposition hope.