However, the Portuguese was coy over where Sanchez may feature for United, insisting that he is capable of playing in any role in attack.
At his pre-match press conference, the 54-year-old said: "Everywhere, in the attacking positions. I know him for many many years, I was with him in Italy at Udinese, in Spain, when he was at Barcelona, in England, when he was at Arsenal, so our careers are almost made in the same countries simultaneously, so I know him very very well.
"I saw him play on the right, on the left, as a striker and behind the striker, these are Alexis' positions.
"I saw him play different tactical systems, different philosophies of different managers, I saw him successful in every country with every manager and every position so he's a player that becomes more than a player because of that motivation, he can play in four different positions."
Sanchez has not made an appearance in a competitive match since coming on as a substitute in Arsenal's EFL Cup fixture with Chelsea on January 10.