The South Korean, who already has four Premier League goals this season – all of which came against Southampton – had to be withdrawn at half-time of Sunday’s 1-1 draw against the Magpies after tweaking his hamstring.
At the time, Mourinho claimed Son would be out ‘for a long time’ and feared it was the first of many injuries Spurs would sustain during a gruelling run of games.
The north Londoners played on Tuesday night against Chelsea in the Carabao Cup, winning on penalties, and just 48 hours later take on Maccabi Haifa in the Europa League before visiting Old Trafford on Sunday.
Son was not involved against Chelsea, nor will he play any part on Thursday, but Mourinho has opened the door for the 28-year-old to potentially return against United – though the chances are slim.
‘Sonny of course is not playing tomorrow. He’s a doubt for Sunday,’ explained the Portuguese coach at his pre-match press conference ahead of facing Maccabi Haifa.
One player who definitely will not be involved is Gareth Bale, with Mourinho saying the Welshman is still a couple of weeks away from getting back up to full match fitness having picked up an injury during the last international break.
Mourinho continued: ‘Bale, he cannot play, tomorrow or even on the weekend – that I can confirm. He’s working very hard, very committed, very professional, very happy, but not yet for tomorrow or for the weekend.
‘I believe that the two weeks of internationals can be important weeks to his last phase of recovering and fitness problem, hopefully to play when we’re back to the weekend after national teams.
‘Let’s see if it’s possible to arrive there. And from yesterday, just fatigue, no injured players.’