The Brazilian had often been touted as a target for the Saudi Pro League, though he had managed to retain his place in the Red Devils squad and will leave of his own accord.
Right time for Casemiro
At 34 years of age, the time now seems appropriate for the Brazilian to step aside, though he can do so with his head held high.
He joined United in the summer of 2022, and it's difficult to argue that during the four years since, he's become one of the club's most important players.
Both his experience and his value to the squad have always been very much in evidence, not to mention that 22 goals and 13 assists from a defensive midfielder stand out.
Particularly when you consider that in the same time frame, only Rasmus Hojlund (26G, 4A), Alejandro Garnacho (26G, 19A), Marcus Rashford (45G, 17A) and Bruno Fernandes (55G, 58A) have more.
Big card count
As might be expected when a player begins to age, their timing is a little off. Casemiro's card count of 35 yellows and three reds in all competitions (the most in the squad in both cases since he signed for the club) would be subtle evidence of the same, though there is also a cogent argument that a player in his position should actually be putting themselves about.
In terms of his other attributes, little has been said about his consistency in terms of appearances, for example.
To date, the Brazilian has made 152 appearances (130 as a starter) at the club, totalling 11,205 minutes. Only Diogo Dalot (173 appearances, 160 as a starter, 14,268 minutes) and Bruno Fernandes (191 appearances, 186 as a starter, 16,682 minutes) have more.
An excellent passing range is also overlooked, with his 2,088 passes into the final third only surpassed by Bruno's 4,735. It's a similar story with forward passes more generally, as Bruno's 3,423 is the only better return than Casemiro's 2,721.
Superb passing and defending
An 81% passing accuracy is in keeping with what United and Real Madrid will have demanded of him, and the fact he's also created 147 chances (only Bruno, Dalot and Christian Eriksen have more) is also worthy of praise.
Though Bruno is, again, the only player to have attempted more one-on-one duels than Casemiro (1,794 to 1,593), the Portuguese has actually won fewer (843 to 879), giving the Brazilian a higher 55.2% success rate.
Aerially, no one has attempted more than Casemiro's 444 headed duels, and only Harry Maguire has won more (312 to 254).
450 tackles, 260 of which have been won, are also best-in-class showings from the 34-year-old, who has, reportedly, told the United hierarchy that they should sign his international teammate, Bruno Guimaraes, as his replacement.
Guimaraes integral to Newcastle
The Newcastle United captain joined the club six months earlier than his countryman had made the switch from the Santiago Bernabeu to the Theatre of Dreams, and became an instant hit with the Geordies.
A never-say-die attitude and a willingness to get about the pitch and get stuck in are all attributes that have endeared him to the St. James' Park faithful.
He's so integral to anything that the Magpies do that it's no wonder they've already slapped a 'not for sale' sign on him.
But just how well does he measure up to Casemiro?
More goals and assists
31 goals and 32 assists give him the edge in this regard, whilst 44 yellows but no red cards indicate a competitive style, and often playing right on the edge of what's considered acceptable in what is, after all, a physical game.
With 172 appearances, 159 of which have been as a starter, no one at the club has more since Bruno joined. As expected, his 14,311 minutes played to date are also the most in the Newcastle squad.
3,285 passes into the final third can't be beaten either, though 2,740 forward passes more generally see him drop from his perch quite significantly.
Only Kieran Trippier (288) has created more than his captain's 234 chances, but Bruno's pass completion rate of 84.5% from 8,701 total passes sees him as the leader once more.
Can the Red Devils afford him?
2,033 one-on-one duels have been attempted by Bruno, with 1,100 of them won, and 1,003 ball recoveries made, putting him way out in front in these metrics too.
Heading definitely isn't his forte, with only 77 of his 179 aerial duels being successful; however, he could consider himself redeemed by the fact that he's attempted the most tackles (370) and won the most (220) in the squad.
All in all, the 28-year-old would be a superb potential replacement for Casemiro, but whether the Red Devils can offer enough to tempt the Magpies into selling their prized asset is another question entirely.
