Jose Mourinho has mocked Frank de Boer as "the worst manager in the history of the Premier League" after the former Crystal Palace boss questioned his handling of Marcus Rashford.
England forward Rashford scored two wonderfully taken goals as he starred decisively in United's 2-1 Premier League win over bitter rivals Liverpool on Saturday – his first top-flight start since Boxing Day.
De Boer, who was sacked as Palace manager last September after failing to muster a goal or a point over the course of four games in charge, said it was a "pity" the 20-year-old had Mourinho as a manager, as the Portuguese would deny him the game time he required.
The United boss had an acerbic response to hand when he addressed a news conference ahead of Tuesday's 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.
"I read some quote from the worst manager in the history of the Premier Leauge, Frank de Boer," Mourinho began. "Seven matches, seven defeats, zero goals.
"He was saying it is not good for Marcus Rashford to have to be coached by me.
"If he was coached by Frank he would learn how to lose because he lost every game."
Mourinho went on to credit United's academy staff and his predecessor Louis van Gaal for their role in Rashford's development and insisted the player remains in safe hands under his own leadership.
"We try to give the best to the kid's education. 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.
"If you go to his numbers and how many matches he played with me last season and this season, maybe I am wrong, but I would say he is probably in the top five players with the most matches over two seasons.
"The best thing that can happen for a kid is to have experience and Marcus is having these experiences."
Rashford is set to feature in England's squad for the 2018 World Cup in Russia 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.
Southgate has discussed Rashford's progress with the man at the helm at Old Trafford, and Mourinho insists the England boss is satisfied with the current state of affairs.
"I think that Gareth Southgate doesn't mind that I say a couple of minutes of our conversation were about Marcus," said Mourinho.
"I think we were all on the same page. He [Rashford] played for Manchester United many, many, many times. He starts some and comes from the bench in others. He is 20 years old.
"Does he play every match from the start? Of course not but he is a player that we trust. I said that before the Liverpool match when many of you were maybe not expecting him to start.
"He started and had a good match and I'm not just talking about goals. I'm really happy with Marcus."
|Kenyan Drake on Miami Miracle: I couldn´t let Gronk tackle me!|
|Ronaldo: I deserved Ballon d´Or, the numbers don´t lie|
|Rugby Australia to make Cheika decision this month|
|England defender Gomez signs new Liverpool deal|
|Ronaldo wants to see Messi follow him to Italy|
|Neymar happy to play in any position for PSG - Draxler|
|Paine insists he is ´fine´ after taking blow to finger|
|Ponzio: River players will be ´idolised´ for Libertadores success|
|Champions League permutations: How Inter, PSG and Liverpool can progress|
|Kohli: India were better and deserved to win|
|Bears shut down Goff, Rams|
|India survive dramatic finish against Australia|
|Klopp calls for electric Anfield atmosphere against Napoli|
|Saints clinch back-to-back NFC South titles, Bears trump Rams|
|Bucks improve to 2-0 against Raptors with win in Toronto|
|Black Caps include Patel for Sri Lanka Tests|
|Maidana: River want Real Madrid clash|
|Cowboys top Eagles in OT behind stellar Cooper display|
|AC Milan evaluating Fabregas signing – Leonardo|
|WATCH: Steelers´ chance at game-tying field goal slips away|
|Hayne will plead not guilty to charges, says lawyer|
|Boca boss Schelotto: The only thing I feel is sadness|
|Cardinals´ Fitzgerald makes NFL history with most receptions for one team|
|River Plate´s Copa Libertadores star Gonzalo Martinez confirms January departure|
|Klopp: I was never worried about Salah´s form|
|Packers QB Rodgers sets NFL record for most passes without an interception|
|World Cup bulking hampered Man United form – Lukaku|
|Leonardo rules out Ibrahimovic Milan return|
|Warriors´ Green to return against Timberwolves|
|I feel for him… we´ll make it work – Butler responds to Embiid´s frustration|
|Torino draw no missed opportunity for misfiring AC Milan, claims Gattuso|
|We´ll always be linked together forever - Wade reflects on playing with James before final match-up|
|O´Sullivan wins record seventh UK title|
|Chiefs secure playoff berth, Saints win NFC South|
|River Plate 3 Boca Juniors 1 (aet, 5-3 agg): Quintero and Martinez clinch Libertadores title in extr|
|WATCH: Chiefs QB Mahomes throws no-look pass|
|Dolphins defeat Patriots on miraculous final play|
|Kizzire eagle snatches QBE Shootout victory|
|AC Milan 0 Torino 0: Donnarumma shines, Cutrone misses late chance|
|Back to the drawing board for West Indies - Chase|
|Copa Libertadores: Messi and Griezmann among stars in Madrid for River-Boca Superclasico|
|Brady sets NFL record for most career TD passes|
|Copa Libertadores: Tevez named on Boca bench for Superclasico final|
|Premier League needs VAR, right now! - Benitez fumes over Dean´s decisions|
|McCall expects Itoje to fit for the Six Nations|
|Solari salutes Real Madrid character after ´ugly´ Huesca win|
|Berbatov defends under-fire Lukaku|
|Sarries crush Blues to maintain unbeaten start|
|Newcastle United 1 Wolves 2: Doherty punishes Yedlin red with late winner|
|Deeney jokes he´ll ´smash´ former Watford star Richarlison|
|Huesca 0 Real Madrid 1: Bale ends drought as Solari´s men edge to victory|
|Ponting: Umpires not looking at no-balls|
|Bale ends longest LaLiga goal drought|
|Porter backs Brees for MVP, Saints for Super Bowl|
|Verstappen eyeing 2019 title fight|
|Wall ´shouldn´t have played´ against Cavaliers after scoring just one point|
|Hazard: Man City the best team in the Premier League despite Chelsea win|
|LeBron explains why he gave a Grizzlies employee his game-worn shoes|
|Bangladesh cruise to ODI victory as seamers punish Windies|
|Football will win over violence, claims CONMEBOL president|
|Alcorcon support Reus Deportiu over unpaid players|
|Saponara explains cheeky celebration after last-gasp leveller|
|Godin and Filipe Luis return to Atletico training|
|Kick It Out condemns alleged racist abuse of Sterling|
|Emotional Oosthuizen clinches South African Open title|
|The Sunday Seven - 7 Key Opta facts for NFL Week 14|
|Martino salutes Atlanta´s grand plan|
|India´s tail must show greater application - Bangar|
|Mourinho: Diogo Dalot can be new Gary Neville|
|Sterling hits out at media coverage of black players|