George Kruis faces a battle to be fit for England's upcoming Tests after the Saracens lock underwent minor ankle surgery.
Sarries on Friday confirmed that the second-row will be out for "a number of weeks" following an operation, giving England head coach Eddie Jones another headache after a host of players had already been ruled out of four internationals in the next six weeks.
Kruis, a key player for club and country, has also joined the injury list just three weeks before the Six Nations champions lock horns with South Africa at Twickenham on November 12.
Saracens director of rugby Mark McCall said: "After consultation with George and England we are in all in agreement that it's in the best interest of the player to undergo this minor procedure now with the majority of the season still ahead of us.
"George is on the road to recovery and we look forward to his return to action sooner rather than later."
England face Fiji and Argentina next month before coming up against Australia on December 3.
Kruis' setback is also a blow for Premiership and European champions Sarries, who face Scarlets in the Champions Cup on Saturday.