England co-captain Dylan Hartley could miss most of the Six Nations because of a knee injury.
Hartley has not played since December 21 because his knee is "grumbling," according to his Northampton club.
It's serious enough that Hartley was left out of England's 35-man squad for the championship announced on Thursday. He will miss the training camp in Portugal this week and the first two matches next month against titleholder Ireland and France.
Coach Eddie Jones has penciled in Hartley for the third round against Wales on February 23, but admits even that is optimistic.
Jones said flyhalf Owen Farrell will captain England on his own.
Hartley remains an integral part of Jones' plans, even though he lost his starting position at the end of the November internationals: Jamie George started at hooker against Japan and Australia.
Former captain Chris Robshaw was also left out of the squad. He's close to making a comeback from knee surgery which ruled him out of the November tests, and could be available for the France test on Feb. 10.