Ex-Arsenal manager Arsene Wenger has issued a warning to Manchester United about Alexis Sanchez, according to the report in BeIN Sport.
Wenger managed Sanchez at Arsenal before the Chilean forward forced a move to Manchester United in January.
Wenger says Manchester United should never write off the former Barcelona forward.
"It is the question that he has raised with his performances, I believe he has lost confidence”.
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"The strength of Alexis Sanchez is to take initiative, to dribble, to take people on.
“These kind of players are most vulnerable when they have no confidence anymore because their game is based on confidence and feeling free to take initiative.
"He has lost that slowly, even with the interruption of the season, since the start of the season he looks like he had a high level of energy that he has lost as well.
"Certainly, he is refreshed now because Mourinho left him out for a while and he has a good opportunity to get back to where he belongs, as a top player,” Wenger said on BeIN Sport.
Sanchez scored against Newcastle United at the stoppage time to earn The Red Devils three points after trailing by two goals at the Old Trafford in the Premier League three weeks ago.
Wenger is out of a job at the moment but he aimed to return to football management next year, it is speculated that Real Madrid is one of the teams vying for his signature.