The English defender was hauled off in the 58th minute at Old Trafford after picking up what appeared to be a muscular strain during the comprehensive defeat by Spurs.
A goal from Harry Kane and two from Lucas Moura in the second half handed Spurs all three points and sent Manchester United crashing to their second straight Premier League defeat of the season.
And Mourinho revealed after the game that the Red Devils are waiting to find out the extent of the problem suffered by the England defender.
Speaking at his post-match news conference on Monday night, Mourinho said: “I don’t know what Phil Jones has – maybe a hamstring but I did not speak yet to know what it is – but we have Smalling, Lindelof and Eric Bailly.”
Manchester United will now look to return to winning ways when the Red Devils travel to Burnley in the top flight on Sunday afternoon.
Mourinho will be aiming to steer the Red Devils towards a Premier League title challenge after they finished in second place in the table last term and without a trophy.
Manchester United have not won the Premier League title since back in 2013.
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