Former Manchester United striker Andrew Cole has labelled the impact of Casemiro as "absolutely frightening".
The Brazilian joined United from Real Madrid in August and has been a key figure as Erik ten Hag's side compete on four fronts.
Casemiro scored the opening goal in Sunday's 2-0 EFL Cup final win against Newcastle United and was named man of the match at Wembley.
Cole said: "[His impact has been] Massive, absolutely massive.
"We always believed that we needed a player in that position, but I don't think anyone could expect him to have come in and done what he's done.
"I think he's been absolutely frightening.
"We know about his experience. What he's achieved at Real Madrid, and playing for the Brazilian national team is so big, so he's a pivotal player for Manchester United.
"You see [in the EFL Cup final] what you've seen throughout his time in the Premier League so far. What he brings to that team, he brings a hell of a lot of quality to the team."
Cole was part of the United side in 1998-99 that won a historic treble of Premier League, FA Cup and Champions League, and with Casemiro arriving at Old Trafford a year after Raphael Varane had also joined from Madrid, he is in no doubt that the pair's success at Los Blancos has helped the existing squad.
"They can help in that way if you're buying into it as a team of serial winners... things do come a little bit easier," he said. "So it's nice that those players are in the side... World Cup winners, Champions League, winning La Liga many times between them, you need that in a dressing room.
"I think if you look at Manchester United as a team it is very infectious, everyone's celebrating and everyone will believe in everyone buying into the cause.
"I can look at my time also at Manchester United playing under Sir Alex Ferguson, that's where you wanted all of us to believe in it, all of us to buy into it and once you cross that white line, we're a team and we play together as a team, we stick together as a team.
"And looking at this Manchester United team, Ten Hag has definitely got that right."
Cole also hailed the form of goalkeeper David de Gea, who kept a clean sheet in the EFL Cup final.
"If you look at De Gea, his performances over the past few years and again this season, he's producing saves when Manchester United need those saves, he's keeping Manchester United in games and keeping clean sheets," Cole added.
"We can talk about all the other things, he's not the best with his feet or this kind of nonsense but as a goalkeeper you've got to keep the ball out of the net and that's what he does.
"He made two massive saves [against Newcastle], made a big save at nil-nil from [Allan] Saint-Maximin, then he makes another save to close it out at 2-0 and those kinds of things people are not talking about.
"Saint-Maximin scores and Newcastle goes 1-0 [it's a] different game, so I keep saying, as I have said I think over the past few seasons, he's been massive for Manchester United."
