Casemiro's time at Manchester United has generated a mixture of initial praise and subsequent criticism from pundits and fans. But apart from Erik ten Hag and his team-mates, no one truly knows how he operates behind the scenes.
While it may be difficult to get an honest view from those currently at the club, Will Fish - who left Old Trafford on a permanent transfer this summer - has offered a candid take on the Brazilian star's conduct.
The 21-year-old recently left United to sign for Cardiff City in a permanent deal, with the Red Devils receiving a £1million fee that could rise to £3m. It's reported United inserted a buy-back option into the agreement and will take a 30 per cent cut from any future sales.
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But before that, having spent two years on loan at Scottish club Hibernian, he was finally given a chance to prove himself in pre-season on their tour of the USA.
With several players still on holiday following Euro 2024 and the Copa America, he was given the opportunity to flourish in the backline. Casemiro was patrolling the midfield in front of him and Fish was left in awe with what he witnessed.
"At United, I expected to be involved in the first team because a lot of players were still away. I started the first game alongside Jonny [Evans] and thought I handled myself well in pre-season," Fish told The Athletic.
"We lost to a late goal, but we’d only been training for a few days while Rosenborg were match-fit and in the middle of their season. Casemiro was in front of us. Mason Mount and Rashford played.
"I observed Casemiro. He was so professional: always in the gym before training. On the pitch, he sees the game differently. He’s one step ahead, always wants the ball and passes around the corner."
Fish was born and raised in Manchester, and had been at the club since the age of seven, so few players know about which players have the 'United DNA' ingrained into them better than him.
His opinion on Casemiro may not be shared throughout the club's fanbase, however, after the 32-year-old's dismal first-half display against Liverpool last time out.
The Red Devils were humbled 3-0 by their long-time rivals at Old Trafford and Casemiro was arguably at fault for both goals conceded before the interval.
His sloppy pass was intercepted, allowing Mohamed Salah to score. Then Luis Diaz took full advantage when the defensive midfielder was easily shaken off the ball, leading Ten Hag to take him off at the break.
That came after another poor display at Crystal Palace last season. Despite his recent woes pushing him closer to the exit door, the former Real Madrid midfielder is yet to secure a move away and is determined to fight for his place after turning down a loan move to Galatasaray.
Fish's comments at least show there is some backing from his team-mates. As Casemiro looks to turn his season around and win back his manager's trust, that sense of professionalism will be put to the test.