"Rashford is without doubt one of the biggest talents in the Premier League and could play a big part in Russian Federation (at the World Cup) this summer".
YOU can lambaste Jose Mourinho for his - at times - pragmatic approach to football or if you disagree with how he deals with the press but one thing you cannot question is his approach to Marcus Rashford.
That prompted a furious reaction from the Red Devils boss as he mocked De Boer's ill-fated spell in charge of Crystal Palace.
"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".
No player has featured more times for United in Mourinho's time as manager than Rashford.
"If Marcus would be coached by Frank, he would learn how to lose".
24 hours after one of the most brutal managerial insults, De Boer's twin brother Ronald has tried to play peacemaker as he insisted that Frank has the utmost respect for Mourinho. "But Mourinho is not like that". He wants to get results.
Here, we take a look at some of the factors that may influence whether Mourinho gives the young forward more opportunities.
You could see he wasn't right - everything which was easy for him previously became a difficulty and Rashford's natural game had vanished as a outcome of not having a rest. He has three goals in this season's Champions League and with vital games against Sevilla in the knock-out stages of that competition, an FA Cup quarter-final against Brighton and a huge derby clash with Manchester City all coming up in the next four weeks, Rashford could be Mourinho's go-to man once more.
Yet, some labelled him as a fringe player simply because Alexis Sanchez's arrival gave Mourinho the opportunity to rest a 20-year-old who had played nearly every game for United. Of course, with Marcus, I have to be honest and give the credit to the people in the academy who were responsible for his formation; I have to leave credit to Louis van Gaal, who was responsible for his first season in the first team.
What a ridiculous concept, especially when the slightest bit of homework would have made them realise just how important Rashford is to Mourinho and United.
United host Sevilla in Tuesday night's Champions League last-16 second leg with the tie poised at 0-0, meaning the Spanish club will go through on away goals in the event of a score draw.