Spurs and United were evenly matched until Romero’s rash tackle on Casemiro saw him sent off, paving the way for Bryan Mbeumo and Bruno Fernandes to seal a 2‑0 win for the Red Devils.
Romero’s challenge would typically result in a three-match ban, but he will be absent for game as he has already been sent off once this season.
And he has been criticised by former Premier League striker Chris Sutton, who claims the centre-back “killed his team” against Man Utd.
“Romero’s focus should be on playing football first and foremost. today he killed his team making that challenge,” Sutton said on BBC Sport.
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“People have been throwing the blame for Tottenham’s problems at the manager but there’s a guy, a World Cup winner, that should be leading by example.”
Spurs goalkeeper Guglielmo Vicario, meanwhile, confirmed after the match that Romero “apologised” to his teammates.
“He is disappointed because he knows this red card could have been avoided so he apologised,” Vicario said.
He is our captain and today he made a mistake but we know the player he is and he is going to come back stronger and help us massively throughout the season.”
Frank also spoke on the red card and explained why he was “very proud” of his players despite the defeat leaving them only nine points clear of the bottom three.
“I think the first 30 minutes were a good away performance at a difficult place against a team with confidence in them and flow. Then after the red card, I am very proud of the players,” Frank said on TNT Sport.
“The resilience, staying in the game mentality, still being a threat at times trying to create something. Very proud of them. Then, of course we just made the three offensive subs and then we concede the second.
“I think the last 60/70 minutes, we were playing with 10 men. They put everything into it. Very proud of the fans. You could hear them loud throughout the game.