Unsurprisingly, Mourinho has not taken too kindly to seeing his methods criticised and has hit back at De Boer, telling reporters: "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".
"When you are younger than I am, and you are learning the game, I think you do need it".
The United boss had an acerbic response to hand when he addressed a news conference ahead of Wednesday's (AEDT) UEFA Champions League showdown with Sevilla, seemingly holding De Boer responsible for Palace's slump extending to seven winless and scoreless matches as Roy Hodgson picked up the pieces at Selhurst Park.
Those words incurred the wrath of Mourinho, who dubbed De Boer the "worst manager in Premier League history" and now the club have come to their manager's aid with the supposed "myth-busting stat".
"If he [Rashford] was coached by Frank, he would learn how to lose because he lost every game", Mourinho said.
De Boer, though, suggested after the game that Rashford would be better off playing under a manager other than Mourinho.
"Does he play every match from the start?"
Huge solar storm set to slam Earth TOMORROW
Moderate storms, known as G2 storms, are somewhat more intense than G1 events, though still not a huge cause for concern. Stargazers do not need telescopes to see the Aurora Borealis with the incredible colours visible to the naked eye.
There has been plenty of talk in recent weeks surrounding Jose Mourinho's handling of Manchester United wonderkid Marcus Rashford.
"Right now, I'm probably not learning the most on the pitch", said the two-goal hero.
Of course, Manchester United's claim ignores the fact that a player is awarded with an appearance whether they play the full 90 minutes or just one.
Despite featuring forty times for United this season, Rashford has struggled for starts with Saturday's derby against Liverpool being the striker's first of 2018.
Senior Republicans urge Trump to back down on tariffs
All three sources spoke on condition of anonymity because they didn't want to publicly discuss industry purchasing trends. Canada is the No. 1 seller of both steel and aluminum to the U.S.
His performances at the end of 2017 meant his demotion to the bench was much warranted and now he has comeback, due to injuries, and shown what he can do against Liverpool with his trademark brace.
"We are not one of the best teams in the competition but when a team arrives in the last eight, anything can happen", said Mourinho.
"When you are in the last 16 it looks really, really far, but when a team gets in the last eight you start smelling the semi-finals".
Russian Federation hits back at United Kingdom , cites 2018 World Cup
In a statement published on Monday, the ministry was quick to condemn the reports, claiming they were for the objective of ramping up "anti-Russian hysteria".