Ben Shaw was seemingly left angered after the Special One dropped the left-back out of the squad for the 4-0 drubbing by Chelsea, reports The Sun.
For the game against his old club, Mourinho called up Marcos Rojo – who Ben dubbed “useless”.
Starting off the rant, Ben initially appeared to wish the club well, saying: “Good luck today Utd.”
However, things quickly turned sour as the team was announced and Shaw was dropped, with Ben allegedly writing: “As if Marcus (sic) Rojo takes Luke’s place on the bench, I’m sorry but he is useless.
“Mourinho didn’t even include Luke in the squad even though he’s fit and healthy, he’s always had something against Luke, knew it.”
Luke’s clearly fiercely loyal brother then looked to get even more aggressive as he wrote: “Stop being such a c**t then maybe you won’t be seeing these numbers.
“Haha the result is laughable and not even finished yet.”
The tweets have now been deleted from the Twitter feed, and Ben seems to have since taken to Twitter to distance himself from the comments.
A message said: “When your tweets are clearly photoshopped and everyone believesthem. Don’t believe everything you see online! Peace.”