MANCHESTER -- Jose Mourinho has accused Henrikh Mkhitaryan of "disappearing" this season and revealed the midfielder has been left out of Manchester United's last two squads as punishment.

Mourinho has confirmed Mkhitaryan will return against Brighton at Old Trafford on Saturday after failing to make the bench against Newcastle or FC Basel.

But the Armenian has been told by the United manager he wants to see a marked improvement after a string of disappointing performances.

The 28-year-old, a £30 million signing from Borussia Dortmund in 2016, started the season with five assists in his first three games, but he has not recorded one in the Premier League since.

He has also been substituted in each of his last eight starts and withdrawn before the 65-minute mark in five of his last six.

Mourinho told a news conference on Friday: "I was not happy with his last performances.

"I'm not speaking about one or two, I'm speaking about three, four or five. He started the season very well and after that, step by step, he was disappearing.

"His performance levels in terms of goal scoring and assists, high pressing, recovering the ball high up the pitch, bringing the team with him as a No.10, were decreasing step by step.

"That was enough because the others worked to have a chance. Everybody works to have a chance. It's as simple as that."

Mourinho was critical of his forwards following the surprise 1-0 defeat to Basel on Wednesday after his team missed a host of chances in the first half.

It was a problem that plagued United last season, although this term they are the second-highest scorers in the Premier League after Manchester City.

Still, Mourinho insists a squad that boasts the attacking talents of Romelu Lukaku, Zlatan Ibrahimovic, Paul Pogba, Marcus Rashford, Anthony Martial, Juan Mata and Mkhitaryan should be producing more.

Jose Mourinho left Henrikh Mkhitaryan out of the last two United squads as punishment for dissappearing. John Peters/Man Utd via Getty Images

He said: "A team that plays the way we play so many times, I think we should score more goals than we do.

"The team that excites more is the team that after five chances is winning 4-0. That's a team that excites more."

Mkhitaryan's return against Brighton -- United's first league game against The Seagulls since 1983 -- means that another forward will have to miss out warned Mourinho.

He said: "He will be back in the group. For him to be back to the group, it means that somebody is going to leave the group.

"Maybe the next press conference after the match you are asking me why a was not on the pitch or why he was not even selected. That's life. Rules are like this. Only 11 plus seven.

"When you have a chance and the performance is not what you expect, that's normal. That's life. You have to perform."

Mkhitaryan has fallen out of favour after starting 11 of United's first 12 games of the season. And he has been told to follow the example set by Martial if he wants to win back a regular place.

Mourinho added: "I think we had an improvement with Martial. He's scoring more goals than last season. That's why he is playing more. He has more minutes on the pitch. When you compete a lot, training is difficult to judge because in the end you train in small groups.

"I cannot say that when you play so much, training is the best habitat to analyse the players.

"I would say on the pitch -- pitch, match, and sometimes in a couple of minutes you see things.

"You don't need sometimes to play 40, 50, 60 minutes for the coach to have feelings and have data to analyse.

"So I would say it's on the pitch, especially on the pitch. Tell me on the pitch what you want to do the next match."