Casemiro is one of the best midfielders of his generation - a status he cemented after bringing the curtain down on his illustrious Real Madrid career to join Manchester United. He was the driving force behind United's run to a third-place Premier League finish and Carabao Cup glory in 2022-23, with club legend Gary Neville describing his impact as "devastating".
There was a caveat to Neville's assessment, though. "£70 million ($85m) and £20m-a-year [contract] for five years is a £170m investment," he said on The Overlap back in March. "That is a massive investment. It’s not a smart or shrewd signing when you look at it from a [big picture] point of view."
Casemiro, who will turn 32 in February, is contracted to remain at Old Trafford until 2026, and there is an option to extend that agreement by an extra year. The man described as "the cement between the stones" by Erik ten Hag was supposed to be United's long-term midfielder enforcer.
It should be a cause for great concern, then, that Casemiro's body seems to failing him just 11 games into the new season. The Red Devils have lost six of those matches, which is why they are now languishing down in 10th in the Premier League table and in real danger of exiting the Champions League at the group stage.
There is plenty of blame to go around, but Casemiro's decline has created the biggest problem for Ten Hag, who may need to take drastic action if he is to revive United's fortunes in the coming weeks.