When Manchester United forked out £70 million to sign Casemiro from Real Madrid last summer, more than a few eyebrows were raised. Yes, they were investing in a serial winner with bags of experience, but they were also handing a four-year contract to a 30-year-old who was targuably already past his peak.
A slow start to life in England only gave extra fuel to critics of the deal, but Casemiro gradually proved his worth. The Brazilian played a vital role in ending the club's six-year trophy drought, and has also been colossal during their push for a return to the Champions League.
Ill discipline has overshadowed his contribution at times, but he has generally done a great job of plugging a gap in midfield that has been a problem for United throughout the post-Sir Alex Ferguson era. Casemiro is aggressive, strong and hard-working, and his tenacity has helped to drive Erik ten Hag's side forward.
Maintaining that level of performance is difficult for any player, especially in a team that is competing across multiple different fronts. And in recent weeks, it's clear that the demanding schedule has taken a toll on Casemiro.
He was hit with a four-match suspension after picking up his second straight red card of the season in a 0-0 draw against Southampton on March 12, and hasn't been the same since. Casemiro was poor across both legs of United's Europa League quarter-final against Sevilla, which they lost 5-2 on aggregate, and underwhelmed in their FA Cup semi-final victory against Brighton.
West Ham's Declan Rice outclassed Casemiro in their battle at the London Stadium, too, as United fell to another costly away loss in the Premier League. The question is: Should Ten Hag be worried?
The Red Devils still have plenty of work to do in order to seal a top-four finish, and the small matter of an FA Cup final date against Manchester City to wrap up their campaign. Beyond that, if United are serious about a return to the glory days they cannot afford to carry any passengers - even when it comes to a player of Casemiro's calibre.