"Zlatan is a huge big player that European football is losing now and forever because he will not be back to this level".
Asked about this, the United boss said: "A report said that Luke asked me why I changed him?"
He said: "If he's available Shaw is always an option".
Pogba has been left out of the starting XI by Mourinho for United's past three games, a shocking turn of events given that run has included a cup quarter-final, a vital Champions League tie against Sevilla and a high-profile Premier League meeting with fierce local rivals Liverpool.
Ibrahimovic was United's top scorer during 2016/17 and Mourinho praised the outgoing 36-year-old after he bid farewell to join LA Galaxy.
Mourinho responded by telling Shaw he wasn't defending well enough, which is the reason he gave in post-match interviews when asked why he had replaced him with Ashley Young.
But Mourinho insists he has done nothing wrong.
"This season and also last season (he had a bad injury)", the United boss said of a player who scored and assisted another for France against Russian Federation on Tuesday.
"He has better players than I did at the time".
But we're back. Two weeks later and we have some Premier League matches upon us once again.
The Dutch manager also blasted Mourinho for his unfair treatment of former Bayern Munich midfielder Bastian Schweinsteiger. "He said I was the king of coaches, not the king of football, for my winning periods with Porto, and because when I left Portugal, I opened the door for more Portuguese coaches to leave". Last night I spoke with him a little and thanked him for his nice words. I think this period with Galaxy, these couple of years, probably, will be very good for him.
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"Young had a problem in the last part of the game against Italy, but we think there is a chance for him to recover".