Since Sanchez swapped Arsenal for Manchester United 10 months ago but, since then, the Chile international has failed to produce the same blockbuster form he did at the Emirates.
The 29-year-old’s goal against Newcastle earlier this month was just his fourth for the club, with previous strikes coming against Tottenham, Huddersfield and Swansea.
Alexis Sanchez remains a far cry from his usual self and recent reports have claimed United may offload him when the transfer window reopens in January.
And Arsenal legend Pires believes the player has had ‘complications’ with Mourinho upon signing.
“Yes, he’s going through a complex moment,” he told Chilean newspaper El Mercurio.
“The relationship with the manager is always important, but it’s notable that there are complications between Jose Mourinho and him.
“When you’re a United manager and you have players like Paul Pogba and Sanchez, you have to take care of them, because in the end the only important thing is for the team to win.
“When there are problems, the most important and complicated thing, at the same time, is to sit down to talk and say things face to face.
“Sanchez doesn’t deserve to be on the bench or stay at home.
“We’ll see if he finds a solution in January, because he is not playing and he has to do it, since he is a wonderful footballer.
“Mourinho and Josep Guardiola are two coaches who know how to win and conquer titles, but now, City’s way of playing is higher than United’s and it could be that if Alexis went to Pep’s team his situation would be different.”
Pires also believes Sanchez was wrong to leave Arsenal for United in the first place.
“Alexis was very good, he’s an excellent footballer, but I also got to know him as a person and I can say that I loved knowing him, he is a friend,” he added.
“He stands out for his professionalism and that helped Arsenal to win several titles.
“Honestly, it surprised me.
“For me, Sanchez had to stay at Arsenal, where he was one of our stars.
“I don’t know if he could say no to United, but I think the style of play of the London club suits his performances better.
“But you have to respect his decision.”
Do we?