Manchester United’s 6-3 defeat in the Manchester derby was a crushing blow, but it highlighted one of United’s key issues under Erik ten Hag, a lack of rotation.

After 4 successive Premier League wins, including games against Arsenal and Liverpool, confidence was high. Manchester City’s brilliance certainly contributed to the capitulation that the Reds showed on Sunday, but the team selection was perplexing.

It led to a shocking result. Many picked Manchester City to win, sure. However, the 6-3 scoreline is a favor to United, as Anthony Martial added two late goals after Pep Guardiola took off his star power up top.

Manchester United need to play their best players

One of the issues at Old Trafford in recent years has been the fact players have held starting XI spots based on reputation. Ole Gunnar Solskjær would have played Marcus Rashford on one leg if he could have gotten away with it. As such, it feels somewhat counter-intuitive to criticize Ten Hag.

The Dutch coach rewarded Scott McTominay for his uptick in form with an extended run in the Manchester United team. This has come at the expense of summer signing, Casemiro. You have to admire loyalty to a point. However, in this case it was downright bizarre not to play the Brazilian.

Manchester City are clearly the best team in England, perhaps all of Europe and the world. Liverpool’s fall from grace left the Blues virtually unchallenged. If they don’t win the Champions League this season, then there should be serious questions asked of Pep Guardiola.

With that being said, when you’re going up against a team with such talent, you need to play your best players. Casemiro isn’t a player who is going to gain match sharpness through training and insignificant minutes from the bench.

The Brazilian needs to find his rhythm on the pitch. To do that he must start matches. You can’t adapt to a new team from the bench.

Lack of rotation at Manchester United

The need for a natural holding midfielder at Old Trafford has been clear for a while. Fans have been at pains watching their team persist with a double pivot of Fred and Scott McTominay. Casemiro arrived in order to put an end to that. The Brazilian has been the absolute best at the position for the last three years. He shielded a weakened Real Madrid defense expertly since Sergio Ramos left.

Photo by Catherine Ivill/Getty Images

Photo by Catherine Ivill/Getty Images

Manchester United’s defense improved since another Real Madrid player, Raphael Varane, arrived. He and fellow newcomer Lisandro Martinez replaced Harry Maguire and Victor Lindelöf.

You can get away with not expertly protecting that pairing in easier matches. Although, Manchester City is not an occasion where you can play without a defensive midfielder.

Kevin de Bruyne had so much space in the pocket between midfield and attack and was able to quietly control the game. His passing spread Manchester United’s defense too wide. Plus, Diogo Dalot was not up to the task of limiting Jack Grealish.

McTominay and Christian Eriksen were both being used as box-to-box players, which is a compliment to their respective work rates. Yet, such a strategy left United’s defense exposed against the most potent center forward around.

Ajax saw Erik Ten Hag’s lack of rotation too

Ajax fans were notably critical of the Dutch coach’s selection choices at times in his spell in charge. Ten Hag’s unwillingness to rotate has followed him to Manchester United.

You can’t not adapt on a game-by-game basis in the Premier League. It just won’t work. Manchester United didn’t miss Casemiro in other matches, but pragmatism is a requisite against Manchester City.

The marks for Ten Hag’s early United career are strong. Defeats to Manchester City can happen but the scale of Sunday’s result was preventable. Casemiro’s settling in period must now surely come to an end. Erik Ten Hag needs to be more flexible, even if it hasn’t brought him success in the past.

PHOTO: IMAGO / Sportimage