After Saturday's 2-1 victory over Liverpool, in which Rashford scored United's goals, De Boer said it was a "pity" Mourinho was the 20-year-old's manager. "He wants to get results", De Boer said on BT Sport's Premier League Tonight on Saturday. "There are only 11 players that start - it's just one of the those things".
"Mourinho may not be the only manager under pressure to compete with City but United are the only team in the top four who are not enjoyable to watch", Redknapp wrote in the Daily Mail.
The former Crystal Palace manager told BT Sport that it is "a pity" Rashford plays under Mourinho after the England worldwide marked his first league start of the year with both goals against Liverpool.
Manchester United manager Mourinho called former Crystal Palace boss Frank De Boer "the worst manager in the history of the Premier League" after he said it was "a pity" Rashford is managed by Mourinho.
The England worldwide seized his chance to shine in the Manchester United team with both goals in an impressive 2-1 win over their bitter rivals.
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Across the Premier League and in Europe he has been on the pitch for nearly 1,700 minutes.
On Saturday, Rashford marked his return to the side with two goals against Liverpool, and Jose Mourinho has made a decision to reward the England global with a second outing in three days. He delivered three trophies, albeit two second-rung trophies in the Community Shield, EFL Cup and Europa League, but more importantly, has lifted United to second in the table this season, after disastrous performances under David Moyes and Louis van Gaal. "His season could have been better than what it has been so far".
"I read something, some quote from the worst manager in the history of the Premier League, Frank de Boer, saying it's not good for Rashford to have a coach like me", the Red Devils tactician said.
Lingard, meanwhile, has shown that he can be an integral part of the United first-team and has bagged goals in crucial games. "But when a team reaches the last eight, anything is possible".
Rashford is set to feature in England's squad for the 2018 World Cup in Russian Federation and might be granted a more prominent role than expected as Gareth Southgate waits to find out the severity of the ankle injury Harry Kane suffered during Tottenham's 4-1 win over Bournemouth on Sunday.