Maro Itoje could miss the start of England's Six Nations campaign after Saracens confirmed the influential forward fractured his jaw in Sunday's Premiership defeat to Harlequins.
Itoje, a key man for club and country, was forced off in the second half of Sarries' 20-19 loss at the Twickenham Stoop following a collision with team-mate Mike Brown.
Saracens have now confirmed a break in the 23-year-old's jaw, although it remains to be seen how long he will be sidelined for, with less than nine weeks to go until England open their Six Nations campaign against Italy.
A statement from the European champions read: "Scans have confirmed that Saracens forward Maro Itoje fractured his jaw in Sunday's round 10 Aviva Premiership clash against Harlequins.
"The 23-year old England forward left the field in the 48th minute of Saracens' 20-19 defeat at the Twickenham Stoop and was taken to hospital where scans confirmed the fracture.
"Itoje will now see a second specialist later this week to confirm his return-to-play schedule."
While Itoje's availability for England's Six Nations campaign remains unclear at this stage, his injury undoubtedly represents a major blow to Saracens, who face back-to-back European Champions Cup matches against Clermont Auvergne over the next two weekends.