Saracens and England prop Mako Vunipola is in danger of missing the 2017 Six Nations due to injury.
Vunipola’s injury was revealed after Saracens came out on top in their Premiership win over Newcastle Falcons on Sunday, with the defending champions winning comfortably 21-6.
The loosehead prop’s setback to his knee came the week before in the Champions Cup win over Sale Sharks.
Saracens are already without Vunipola’s brother, England number eight Billy Vunipola, after he was injured during the November Tests earlier this year.
“It’s not looking good [for Mako] to be honest,” Saracens boss Mark McCall told the BBC.
“He’s got to go and see his consultant in four weeks’ time, and then we will determine how long he will actually be out.
“We have to let the injury settle down as much as possible to have any idea because otherwise you are just guessing.
“It’s a big blow to lose Billy and then Mako. Both are such important players or us. We were going to lose them for the Six Nations but to lose them in the run-up to that is so disappointing.”