For a coach, especially a new one who needs time to convey their guidelines, it is generally advisable to maintain as much continuity as possible at the center of the defence.
There are areas of the pitch where rotations are more frequent, sometimes even necessary, but in front of the goalkeeper, theoretically, there should be as much stability as possible once the key players are identified.
This is because cohesion is needed; it requires memorizing timing and the characteristics of one’s teammate. This season, Fonseca hasn’t been able to provide that continuity due to some physical issues.

Sometimes, though, he chose not to: for instance, Pavlovic, after a promising start, found himself on the bench. And so, at a certain point, someone who was previously last on the list emerged. Malick Thiaw’s rise is nothing short of a resurrection, considering he was initially the fourth-choice central defender available to Fonseca.
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Physical issues for Malick Thiaw
Due to recurring physical issues, which began last season when he missed two and a half months with a myotendinous injury, the German defender's return saw him no longer quite the same. A compromised season.
This season also started with struggles: a poor start against Torino in the league opener, followed by an ankle sprain that kept him out for three matches—against Lazio, Venezia, and Liverpool—and during this time, Pavlovic put in interesting performances, but above all, Gabbia had a strong, massive breakthrough. It seemed Malick was destined to stay at the bottom of the hierarchy, but credit must be given to Fonseca for not leaving anyone behind—or at least for trying. Thus, against Udinese, he reappeared in the starting eleven, thanks to the 'punishment' imposed on Tomori by the coach after his insubordination in Florence. From that point on, apart from the Bruges match, Thiaw has been a regular starter, and his crowning moment came on the biggest stage.
The Bernabeu stadium, with double satisfaction: stopping Madrid’s multi-million dollar attack and scoring his first goal in the AC Milan colours, in a match that will remain among the club’s most beautiful European memories.
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Thiaw must continue like this
This summer, it seemed Malick might be on his way out, an idea that remained viable even at the beginning of the season. Now, the story is completely different.
Source: Gazzetta dello Sport on their website
