Jose Mourinho believes Alexis Sanchez's struggles this season for Manchester United are down to injuries.
The Chilean star has managed just one goal and two assists in seven Premier League appearances so far and missed United's 1-0 defeat to Juventus in the Champions League with a groin injury.
Sanchez will also miss the visit of Everton to Old Trafford on Sunday, live on Sky Sports, and Mourinho says he needs a consistent run of games in order to rediscover the form which made him one of the Premier League's most feared attackers while he was at Arsenal.
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"In this moment, he is struggling because he is injured and because he came to the Chelsea match to try to help the team but his physical condition was not good," Mourinho said.
"Then he had to stop and he was not available for Juventus. I believe he is not available tomorrow again.
"So now the point is to be physically in the best condition.
"He arrived in January last season - I don't think that is ever an easy situation for a player.
"But this season he had a good start. He had a good preseason and he started well against Leicester. Then he was injured. Then he came back and then he was injured again.
"So he is struggling with his condition and I think he is the kind of player that needs to really sharp to play his best game."
Sanchez is one of a number of injury headaches for Mourinho ahead of the weekend.
Marouane Fellaini, Phil Jones, Scott McTominay, Jesse Lingard and Diogo Dalot also missed the game against Juventus and it is clear Mourinho is angry with the condition some of them returned from international duty in.
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When asked about his injury list, the United boss replied: "All of them national team. We play against Newcastle and go to the national team period in a good situation, then after two weeks we lost Dalot in Portugal, Fellaini in Belgium, Sanchez with Chile and McTominay with Scotland.
"Some of the national teams were very professional with us and sent the players back, but some of them were not.
"They kept the players and we didn't even know the nature of the injuries. The players arrive two days before Chelsea and we have no idea what is going on."
Lingard has been dealing with a groin injury he picked up while on World Cup duty with England and Mourinho is not pleased with how his recovery has been handled.
"He came from the World Cup with that problem," Mourinho confirmed. "He thought wrongly that the holiday period would bring things to normality, then he thought wrongly that keep working or start working would improve and then he felt in an impossible situation to play football.
"So now he's going back and to do the work to try and be 100 per cent and in this moment he's almost there because of the team's needs.
"Can he help us in the next match? That is the question we have to answer tomorrow. He's almost there."
Lingard's return would be a welcome one for Mourinho who admitted he cannot afford to consider taking out-of-form Romelu Lukaku out of the side.
He said: "If we decide to give a rest to Lukaku, who plays as a striker? Rashford? And then who plays as a winger?
"In this moment we are not in the best situation to think about resting players."
Despite his current lack of attacking options, Mourinho says he would not be tempted to move for Zlatan Ibrahimovic in January.
Asked if a United return was a possibility, Mourinho said: "No".
Asked if it was not an option he would consider, the Portuguese again replied: "No."