The former Dutch global had praised Rashford and said it was a "pity" that he plays for Mourinho, who only cares about results, and not a manager who would continue to play him even if he has a bad game or two.
Jose Mourinho has slammed Frank de Boer as "the worst manager in the history of the Premier League" after the Dutchman said it is "a pity" Marcus Rahsford is playing under the Portuguese at Manchester United.
"Tomorrow is a very hard match, playing against a team that didn't lose against Liverpool home or away [in the group stage], that drew in Liverpool and I say Liverpool because they are an example of a very good team in a big stadium with a big tradition".
"If he was coached by Frank he would be coached how to lose because he lost every game".
"Mourinho is not like that, he wants to get results". Marcus I have to be honest and give the credit to the people of the academy that were responsible for his formation and to Van Gaal for his first season in the first team.
Rashford scored twice in his first Premier League start of 2018 as United edged out Liverpool 2-1 on Saturday, but Mourinho still substituted the 20-year-old England forward 20 minutes from time as he looked to make the game safe. Does he play every match from the start? No.
"But if you go to his numbers and how many games he played with me".
"Frank De Boer, seven matches seven defeats and zero goals".
Mourinho believes United will have a chance of winning the trophy if they progress.
The Portuguese did not actually address that question ahead of the return leg against Sevilla, nor did he give a straight answer on Paul Pogba's availability on Tuesday. Mourinho said he did not know whether the midfielder would be available but Pogba had trained after the open part of Monday's session closed.
Asked if he feels he has the conditions to bring a fourth European Cup to Old Trafford, Mourinho said: "Not yet, but when a team reaches the last eight anything is possible".
Michael Carrick has confirmed he will retire at the end of the season. "That's pretty much where I'm at".
Carrick is set to join United's coaching staff in the summer.