Mourinho said before United’s visit to Celta Vigo for the first leg of their Europa League semi-final that he would prioritise continental football over the pursuit of a top four finish and was considering a weakened side for the Emirates.
Arsene Wenger has never defeated Mourinho in a competitive match but can ill afford not to on Sunday, with Arsenal six points off a top four spot with just a single game in hand.
Even if Mourinho does save his strongest lineup for the second leg of the European tie next week Keane, whose disdain for Arsenal was legendary during his later years at Old Trafford, is convinced the visitors are capable of claiming three points in North London.
“It is clear that his priority is trying to win the Europa League and guarantee Champions League football,” he told ITV.
“I think he is right. With the way the last week has gone, prioritise winning a trophy, definitely.
“Even a weak team would probably still beat Arsenal, they can afford to do that.”
Speaking ahead of the match Wenger conceded that even a weakened United could cause problems for his struggling Arsenal side, who have won just six of their last 16 games.
“I don't know what Manchester United will do,” said the Frenchman.
“Anyway they have a massive squad with quality players. Only a top level performance will get us the win we want.”