England wing Jonny May will miss the opening two fixtures of the Six Nations with a knee injury and will wait to hear from specialists whether he can play any part in the tournament.
May, 31, did not feature for Gloucester against Perpignan on Saturday.
He will miss England's games against Scotland on 5 February and Italy eight days later, but is not yet ruled out of the Wales game on 26 February.
Gloucester coach George Skivington said May is seeing the "best" specialists.
Meanwhile, loose-head prop Joe Marler has tested positive for Covid-19 for the second time in just over two months.
Marler has withdrawn from this week's England training camp in Brighton and gone into isolation.
In November the Harlequins player missed the match with Australia after returning a positive result, but returned to come off the bench in the win against South Africa.
Addressing May's injury, Skivington said: "If he can be back involved in the Six Nations then great. It's unfortunate for Jonny because we'd like to see him playing for England.
"He's had a niggle for a little while and it kept him out of one game a few weeks ago. It's just been chipping away and it got to a point where it wasn't great, so we decided to get it investigated.
"Once we know exactly what the story is we'll have a better idea about the injury. It would have been one incident a few weeks ago, but he's been managing his way through it, as generally speaking senior players do, and it just got a little too much.
"The hope is that he will still play in the Six Nations."
May has scored 35 tries for England, placing him second in the country's all-time standings behind Rory Underwood on 49.
In addition to May, England have lost fly-half and captain Owen Farrell to injury, while Courtney Lawes is unable to train because of a head injury.
Meanwhile the Rugby Football Union has confirmed that the England squad were forced to evacuate their hotel in Brighton following a suspected electrical fire on Tuesday evening.
The team and support staff, who are in Brighton for a training camp, have since relocated to an alternative hotel.
How do influencers make a living? Content creators reveal ways in which to make it a lucrative careerTransfer Gossip Daily? Get your fix of all the latest and biggest transfer stories