Cristiano Ronaldo and Steven Taylor had to be pulled apart by team-mates after an extraordinary half-time bust-up in the tunnel at St James' Park last night.
Barclays Premier League champions Manchester United restored their seven-point lead at the top of the table after goals from Wayne Rooney
and Dimitar Berbatov cancelled out Peter Lovenkrands' early opener.
But England Under 21 captain Taylor could face a suspension for apparently punching Ronaldo on the side of his head in the last minute of the first half and for his part in the confrontation at the break involving several players.
Witnesses said Ronaldo waited for the defender in the tunnel and called him a 'rubbish footballer'. Taylor, it was said, responded by calling last season's Footballer of the Year 'ugly'.
The pair went head-to-head repeating the insults until referee Steve Bennett and United captain Rio Ferdinand were among those who intervened.
Ferdinand was so angry with the original incident that he had chased Taylor to the halfway line and was booked for remonstrating after Bennett had blown for half-time.
Newcastle caretaker manager Chris Hughton said: 'I've had an opportunity to see the incident again and Steven catches him on the shoulder, and that's all it was.'
Sportsmail also understands strikers Andy Carroll and Shola Ameobi were involved in a Newcastle training-ground bust-up on Tuesday. The pair were both on the bench last night.
Newcastle striker Obafemi Martins and Nemanja Vidic were also in the wars, with the latter earning a yellow card for an ugly tackle and then suffering a nasty cut below his right eye when he was caught by Martins' flailing arm in an aerial challenge.
United had to work hard for their 11th successive League victory after going behind in the ninth minute to Lovenkrands' second Newcastle goal. Rooney equalised before Berbatov benefited from Ryan Taylor's dreadful error to score his 13th of the season, 10 minutes into the second half.
United manager Sir Alex Ferguson said: 'You have to show patience and experience. It's nothing new to them. The experienced players are keeping them all right in that respect.'
Newcastle's next two home games are against Arsenal and Chelsea but before that they must travel to fellow strugglers Hull City in less than a fortnight.
'That is a massive game,' said Hughton, who has now won only one of his eight games in temporary charge this season.