Flanker Brad Shields has become the latest injury concern for England ahead of the Six Nations after he was ruled out of Wasps' European Champions Cup clash with Leinster.
Shields, 27, missed the Pool One match at the Ricoh Arena in Coventry with a side strain, adding another selection headache for Eddie Jones as his squad continues to suffer.
Fly-half Owen Farrell remains a doubt since undergoing thumb surgery which led him to miss Saracens' 38-19 win over Glasgow.
Shields became an integral part of the England set-up during the November internationals when he started all of England's Tests against South Africa, New Zealand and Australia.
The New Zealand-born forward has won five caps for England and was expected to add to his tally when he was selected in Jones' 35-man squad for the Six Nations, but now faces a race against time to be fit.
Farrell required a procedure to repair ligament damage in his thumb but is expected to return in 7-10 days -- a short enough recovery period to be available for the beginning of the Six Nations.
Jones nonetheless needs to decide whether to call up injury cover for Farrell before England depart for a pre-tournament training camp in Portugal on Wednesday.
England open their campaign against last year's Grand Slam winners Ireland in Dublin on Feb. 2.