Worcester's England centre Ben Te'o is set to miss the start of the 2018 Six Nations because of the ankle problem which has kept him out since October.
The 30-year-old British and Irish Lions back has made just seven appearances for his club this season.
He has not played since picking up the injury in the Challenge Cup win over Brive on 14 October.
And the Premiership club now say that the injury will keep him out "approximately four weeks" more.
England begin the tournament away to Italy in Rome on Sunday, 4 February, followed by the home game with Wales at Twickenham on Saturday, 10 February.
There is then a fortnight's break before the Calcutta Cup fixture against Scotland at Murrayfield on 24 February, which might be a more realistic target for Te'o.
Warriors, who return to European Challenge Cup at home to Connacht on Saturday, are still missing several key players.
England squad prop Nick Schonert will be out for approximately another four to six weeks with his ankle injury, while flanker Dewald Potgieter (knee) is not expected back until February,
Centre Wynand Olivier (hamstring) will be out for about six weeks, scrum-half Jonny Arr faces five more weeks out following his concussion injury and stand-off Tom Heathcote, who has also missed most of the season with a concussion injury, is to have his problem reviewed in April.