Saracens as England number eight Billy Vunipola was forced off midway through the first half against Edinburgh.
WP Nel's try 14 minutes from time gave the Scots a shock 21-18 away victory over the Londoners in the Challenge Cup.
And the defeat may prove costly as Vunipola was forced off after falling awkwardly early on, while hooker Kapeli Pifeleti was stretchered off a few minutes later.
The England international, who has had more than his fair share of injuries, only returned a week ago after recovering from a minor knee ligament injury he suffered at the start of November.
Vunipola is set to have a scan on the injury today with the Sarries hierarchy hoping for the best but expecting the worst.
A Saracens club official revealed they will provide an update on their two injured players once they know more later today
LIST: 5 more England internationals who could swap clubs next summer
#1.Ellis Genge
Age: 26
Position: Loosehead-prop
Current club: Leicester Tigers
Linked with: Bristol Bears & Saracens
Saracens could turn to the Leicester captain if they fail to agree a new deal with Mako Vunipola, reports the Mail Online. Both loosehead props, who have also been linked with a move to Bristol Bears are yet to agree new terms with their respective clubs.
Ellis Genge of England celebrates after winning with his son Ragh Ellis during the Autumn Nations Match between England and Tonga at Twickenham Stoop on 6 November 2021. Photo: Tom Sandberg/PPAUK
#2.Billy Vunipola
Age: 29
Position: Number 8
Current club: Saracens
Linked with: Bordeaux, Toulon, Racing 92
Bordeaux have put Saracens brothers Mako and Billy Vunipola on their shopping list for a move to the Top 14 next season.Bordeaux boss Christophe Urios is keen on the England pair with loosehead Thierry Paiva talking to La Rochelle and former Northampton Saints No.8 Louis Picamoles set to retire.
#3.George Kruis
Age: 31
Position: Lock
Current club: Panasonic Wild Knights
Linked with: Leicester Tigers & Saracens
The 31-year-old has spent the last year playing in Japan for the Saitama Wild Knights following a trophy-laden 11 seasons with Saracens. A member of the 2017 Lions squad that toured New Zealand, he has said he still has ambitions to add to his 45 England caps
Mako Vunipola of England during the Autumn Nations Cup match between England and Ireland at Twickenham Stadium, Twickenham, London on November 21 2020. - PHOTO: Phil Mingo/PPAUK
Zach Mercer of Bath Rugby during the Gallagher Premiership Rugby Match between Bath Rugby and Sale Sharks at the Recreation Ground on 14 May. Photo: Tom Sandberg/PPAUK