Sometimes the most basic statistics tell the story best of all. When Casemiro starts for Manchester United they win 72% of the time and lose just one in 10 games. When he doesn't start, they win 67% of the time but lose one in four.
Forget the minutiae of numbers that can explain Casemiro's impact on United and what he does so well, the bare stats don't lie. When he isn't involved United find it harder to win games and easier to lose games.
He wasn't signed in time for defeats to Brighton and Brentford, was on the bench for the mauling at Manchester City and was suspended for the defeat at Arsenal when the Gunners rained in 25 shots. You could even add in the 7-0 defeat to Liverpool, when the Brazilian midfielder may well have been absent, given how badly he played compared to the rest of this season.
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There are other examples within games. United were poor at Leeds when they started without him and had to bring him on after 45 minutes against West Ham in the FA Cup. This is a team that finds it hard to operate at the same level when Casemiro isn't playing.
So how they go about navigating four domestic games without him is going to be something taxing the mind of Erik ten Hag this week. After a second red card in three Premier League matches, the 31-year-old will miss games against Fulham, Newcastle, Brentford and Everton.
It could certainly be worse. All of those games are winnable for United and three are at Old Trafford, but how they cope with the absence of a player who has been transformative on and off the pitch since signing from Real Madrid might well condition Ten Hag's plans for the summer.
Within the squad there are limited options for stand-ins. Scott McTominay has usually replaced Casemiro and with injuries mounting, he will probably do so again. Christian Eriksen and Donny van de Beek are both out long-term and are more advanced midfielders anyway.
Ten Hag will hope to get Bayern Munich loanee Marcel Sabitzer back soon to give him another alternative in the middle. Lisandro Martinez could also be pushed into the holding role, having played there for Ajax.
None of those solutions are ideal, however. McTominay was playing well in keeping Casemiro out of the side in the autumn, but the drop-off between the two now is noticeable. The Brazilian is not only a world-class defensive midfielder, but a sensational passer who has been vital to United's ability to progress the ball.
So when he isn't available they miss the control he offers as well as the ability to get them moving forward. It was noticeable in the recent games against Leeds and West Ham that the speed of United's attacking play was slower without Casemiro.
How teams go about filling the gaps left by their very best players is an age-old question. The better the player, the harder it is to find competition or an understudy for him, and United are suffering for that with Casemiro.
It's almost impossible to find a player who performs the same functions as the former Real Madrid man because they would command a similar transfer fee, significant wages and want to play more often.
But these four games will help to tell Ten Hag if he has suitable backups in his squad or if the transfer market will be required to help solve this problem. A younger, more dynamic midfielder was always likely to be on the agenda this summer, but if United continue to struggle without Casemiro, then it might need to be a more natural holding midfielder.
It could also mean that position is bumped up the list of priorities. A striker tops the bill for Ten Hag this summer and rightly so, but he also needs to build a squad capable of challenging on all fronts and that means having strength in depth.
If a summer move is required, then Ten Hag might well look to Barcelona's Frenkie de Jong once again. The 25-year-old looks an ideal foil for Casemiro, but he's stood in for Sergio Busquets recently and looks comfortable in that holding role.
But the next few weeks offer the players currently in Ten Hag's squad the opportunity to put their hand to fill what have become the biggest boots in the United squad.
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