Jonny Evans, Michael Carrick and Rafael are all major doubts for Manchester United's Champions League tie against Real Sociedad, reports the Daily Telegraph.
The Red Devils trio all sat out Manchester United's Monday morning training session prior to their trip to Spain to play Real Sociedad on Tuesday night.
Both Evans and Rafael had to be replaced at half-time of Manchester United's 3-1 win against Fulham due to back and ankle injuries respectively.
Carrick, who missed his first Premier League game of the season on Saturday with an Achilles injury, is also likely to miss United's midweek match against Real Sociedad - with David Moyes unlikely to risk losing his star midfielder for United's weekend clash against Arsenal.
Manchester United midfielder Tom Cleverley also had to be substituted at the interval on Saturday as the 24-year-old had double vision.
However the England international is likely to be in contention for United's Group A clash at the Anoeta Stadium.