Erik ten Hag believes what Casemiro has brought to Manchester United since their 6-3 defeat to Manchester City in October's derby proves how lucky they are to have him.
United signed Casemiro from Real Madrid in August in a deal potentially worth £70million (€78.9m), though it took him a few weeks to get up to speed.
The club announced his arrival shortly after a morale-boosting 2-1 win over Liverpool, which finally saw them put points on the board after losing to Brighton and Hove Albion and Brentford in their first two games of the season.
Initially he failed to get into the team ahead of Scott McTominay, with the defeat of Liverpool beginning a four-match winning run in the Premier League.
But United were then thrashed 6-3 – even finding themselves 6-1 down at one point – by Pep Guardiola's City. Casemiro made his first top-flight start for the club in their next game, and since then only Newcastle United (24) have won more points than Ten Hag's side (23).
United face City again on Saturday knowing a win will take them to within a point of the champions, and Ten Hag was given the opportunity to reflect on what Casemiro has brought to his team since that October humbling.
Asked how much of a role the Brazilian has played in United's improvement, Ten Hag said: "That's quite obvious.
"I said from the beginning, this team needs a six. What is a six? So, control, holding midfielder. He's so important, the cement between the stones.
"It means in defending [he brings] organisation, he knows his position, anticipating, he's pointing players in right position, he wins balls for the team, wins duels.
"But in possession he can accelerate, speed up the game. He has that competence to give that to a top team at a top level, and there are not many players with his quality in the world, he is one of them, so we are really happy to have him because he makes a huge difference."
That loss to City was something of a reality check for a United side who had seemingly made clear signs of progress after their alarming beginning to the campaign.
Ten Hag thanked City at the time for showing United how far behind the best teams they were, and yet their improvement since has been marked.
The Dutchman was keen to insist revenge has not been used as a motivational tool ahead of Saturday, and he outlined United's progress since October comes down to clear coaching.
"How I analysed that game, I expressed honestly that it was a lesson and we took it, and from that point we made huge progress. We have to continue the progress and the process," he said.
"Maybe [talking about the process behind improvement is] boring, but things are like that. That game was a setback, you can all find reasons, but it's not that interesting.
"It's all about how you have to act, deliver, as a coach. You have to take certain steps, you need a clear philosophy, clear direction, then it's about development.
"That's what we are doing, what we did. That's nice, but in top-level football there's never an end point."