The midfielder's sending off followed a VAR review, with referee Anthony Taylor overturning his initial decision to show a yellow card for a tackle that hit the top of the ball first before going into Southampton forward Alcaraz's leg.

As Casemiro was also dismissed against Crystal Palace last month, an additional game will be added to an automatic three-match ban, meaning he won't be able to play a domestic match again until the trip to Nottingham Forest on 15 April.

"When you freeze anything it looks bad - but everyone who knows something about top football knows what is bad and what is fair," said Ten Hag. "And Casemiro is a really fair player. Tough but fair.

"It shows, he had played over 500 games in big leagues and never been sent off. Now it has happened twice."

Ten Hag complained about the lack of consistency in the use of VAR, noting the referee was not sent to the monitor to review controversial incidents in Saturday's game between Leicester and Chelsea.

Despite having a man advantage for almost an hour and managing 17 shots, Southampton were unable to capitalise and remain bottom of the Premier League.

Even before Casemiro's early exit, David de Gea needed to make a brilliant reaction save to turn away Theo Walcott's close-range header.

De Gea then produced a one-handed save after the break when Walcott ran clear of the home defence, while Aaron Wan-Bissaka cleared off the line when Scott McTominay turned a Kyle Walker-Peters cross towards his own goal. In addition, James Ward-Prowse's free-kick skimmed of the top of the bar and Walker-Peters also hit a post with an angled drive.

United had some dangerous moments themselves, with captain Bruno Fernandes' goalbound effort tipped on to the inside of a post by Gavin Bazunu.

The result consolidated United's top-four position, whilst Southampton are effectively three points from safety given their goal difference, with 12 games of the campaign remaining.

Southampton show improvement

Despite their position in the table, Southampton's form is good.

They have now picked up seven points from four games since Nathan Jones was sacked on 12 February.

It represents their most productive run since August and Wednesday's rearranged game with Brentford does offer the opportunity for Ruben Selles' side to climb out of the relegation zone for the first time since the end of October.

Nevertheless, their goalscoring is a concern - in only one league match since August have they scored more than once. They had the chances to improve that statistic at Old Trafford but couldn't make them count.

Casemiro's ill discipline

Casemiro has been one of the key reasons behind United's improvement this season.

But the positivity around the Brazilian is in danger of being undermined by his disciplinary record.

Sent off against Crystal Palace last month for grabbing Will Hughes round the neck following a mass confrontation, his latest red card was also triggered by the intervention of VAR.

Casemiro did play the top of the ball first but Taylor decided the tackle was dangerous.

Ten Hag said Casemiro was emotional in the dressing room afterwards.

"He is disappointed," Ten Hag said.

Unless United manage a successful appeal, the four-match suspension would rule him out of next week's FA Cup quarter-final with Fulham, plus the three Premier League games that follow.