That's according to Stewart Robson.
The former Arsenal ace insists that the want away forward must play.
Arsene Wenger has been calming that Sanchez is not fit enough to feature regularly.
But Robson says that cannot matter against a team like Chelsea, who the Gunners face on Sunday.
Sanchez simply has to start if Arsenal have any chance of winning.
Robson told ESPN FC: "He's their best player.
"Whether he wants to get away to Manchester City or wherever he wanted to go to.
"Alexis Sanchez is Arsenal's best player and has been for the last couple of years.
"If he's fit he has to play because he's the player that can change the game for them."
