It might go down as one of the worst periods in Manchester United's history. Just days after a humiliating home defeat to Brighton in the opening game of this season, the once formidable football juggernaut were again shamelessly demolished by another Premier League minnow, Brentford, as the newly-appointed Erik ten Hag watched his abysmal team concede four comical goals in about half an hour.

Nevertheless, Casemiro was undeterred by what had unfolded at Old Trafford. The unassuming Brazilian midfielder, who had not yet completed his shock move from high-flying Spanish powerhouse Real Madrid to the incredibly chaotic United, texted a very assertive message to his agent, saying: "Tell them I'll fix this."

Much to everyone's surprise, Casemiro has stayed true to his promise.

The 30-year-old has been the undisputed impetus to a stunning reversal in fortunes for the Red Devils, who have recovered from their harrowing start to win their last 11 games at home on the bounce.

Of the 21 games Casemiro has started since arriving from Spain, United have lost only two. According to stats provider Opta, Ten Hag's side had a 70 percent win rate with him starting compared to when he's absent (57.1 percent). He recovers the ball and re-establishes possession for United 15.8 times per 90 minutes, which is a figure that only bettered by in the Premier League by Manchester City star Rodri (17.0).

Among all midfielders in the English topflight since his first league start against Everton on October 9, Casemiro ranks second for tackles (40), second for duels won (77) and second for clearances (22). 

While Casemiro has repeatedly given a defensive masterclass when wearing the United shirt, his amazing contribution to attacking play came to the fore on Saturday night. It was the five-time Champions League winner who stepped up to end Reading's admirable resistance with two goals and sent United to the FA Cup fifth round with a 3-1 victory.

Casemiro's first goal arrived when his compatriot Antony put him through with an excellent defense-splitting pass. The former Madrid veteran demonstrated calm and composure amid the crowded penalty box, beautifully dinking the ball over the onrushing Reading goalkeeper Joe Lumley.

The maestro doubled his tally soon after when he unleashed a sensational strike from outside the box to find the bottom corner. Fellow Brazilian Fred then added a third before Amadou Mbengue pulled one back for Reading from a corner late on, but Casemiro has already made sure United sail into the next round.

"He's magnificent,” beamed Ten Hag, in reference to Casemiro's rousing performance. "We all know he's a great player and that midfield at Real Madrid, with Kroos and Modric, it was great. He's capable of that [scoring goals]. We see him as a part of it offensively and he enjoys it as well.

"In front of the back line, he always takes good positions. And he can deal with the ball, he can give the right pass. So, he can accelerate the game and if necessary, he can score."

United captain Harry Maguire also outlined how big an impact Casemiro has had on proceedings since arriving at Old Trafford last summer. 

"Casemiro is a top player and has been a top player throughout his career," he told reporters. "You don't win what he has won without being that and playing every game in the success that he has had for club and country."

"He is an amazing player and an amazing character, more importantly. To have him around the place lifts the morale. In and out of possession he has really improved us."

The last of the Red Devil's 12 FA Cup triumphs came in 2016 and Ten Hag knows only too well the importance of end the club's worst trophy drought in 40 years. "We are here for trophies, to win titles, but we have a long way to go," observed the unflustered Dutch tactician. But with Casemiro on their side, the United fans could be forgiven for getting carried away.