The left-back collided with Dani Carvajal during England's clash with Spain and was treated for almost seven minutes on the field, prompting fears he may spend a long time on the sidelines. However, according to BBC Sport's Simon Stone, he may yet feature in the showdown with the Hornets.
"Football Association guidelines state a player who suffers concussion should not play for 14 days," Stone wrote. "But Shaw could play after being treated in United's 'enhanced care setting.' The guidelines allow a player to return earlier if seven criteria are met, and United's state-of-the-art medical facilities are understood to meet the requirements."
It's added that Shaw will need to convince United's medical staff that he's ready to feature at Vicarage Road, meaning his return is by no means guaranteed.
Despite the nature of the injury, Shaw was able to post the following on social media after the match:
Spain captain Sergio Ramos also sent his best wishes to the United man:
The news that Shaw is set to return to action soon is a massive boost for the Red Devils, as the left-back has arguably been the team's standout performer in what has been an up and down Premier League season.
Shaw has never previously been able to nail down a position in the team under manager Jose Mourinho, with the coach primarily turning to Ashley Young as a makeshift option last term. But something has clicked with Shaw in 2018-19.
The raids up the wing that made him such an exciting prospect during his time at Southampton have returned, while the 22-year-old hasn't shirked any defensive responsibilities either. It's the best he's played since the broken leg he suffered in 2015.
United confirmed recently that he was named as the club's Player of the Month for August:
Given the way Shaw has battled back from his setbacks, it was galling to see him down in a heap on the field on Friday again and encouraging to read the left-back will be back in action soon.
United visit Vicarage Road on Saturday evening seeking to end Watford's perfect start to the season. The Red Devils are also in action in the UEFA Champions League against Young Boys the following Wednesday.