Ashley Young could find himself in trouble with the FA after appearing to elbow Southampton's Dusan Tadic in Saturday's 0-0 draw at Old Trafford, Sky Sports have reported.
The 32-year-old was seen aiming for Tadic's midriff as Manchester United defended a corner in the Premier League clash.
Young would likely have been sent off had referee Craig Pawson seen the incident, although the Southampton winger did not react theatrically.
United will be without striker Romelu Lukaku - who suffered a head injury in the first-half - for Monday's visit to Everton, and could now lose another player if retrospective action is taken.
It remains to be seen whether the FA will charge Young with violent conduct, but the altercation was unlikely to have been included in Pawson's match report.
However, Burnley's James Tarkowski may serve as an example, having just served a three-match ban for a similar offence involving Brighton's Glenn Murray.
Should Young be suspended, United boss Jose Mourinho will be left with a shortage of players available at the back, with Eric Bailly, Chris Smalling, Antonio Valencia and Matteo Darmian all currently sidelined through injury.
Young has established himself as a key player at full-back for the Red Devils this season, making 20 appearances in all competitions and scoring a brace in a 4-2 win over Watford last month.
But he could be set for a punishment following United's disappointing stalemate on Saturday, which saw them drop to third behind Chelsea in the Premier League standings.