 Harlequins centre Greenwood has won 55 England caps |
Will Greenwood will be out of action for at least four weeks after undergoing an exploratory operation on his shoulder on Wednesday. "Will underwent a scope on a long-standing shoulder problem yesterday," said Harlequins' Mike Scott.
"We are still waiting to hear from the consultant but he will be out for a minimum of four weeks, maybe longer."
Four weeks out would leave the Quins star only one club game before England start the Six Nations against Wales.
Greenwood has been below his best this season but has an outstanding record against Wales.
His fellow England centre Mike Tindall is battling to overcome a foot injury and early forecasts suggest he will not be ready for the Cardiff game on 5 February.
Gloucester centre Henry Paul faces an uncertain international future following his humiliating 26th-minute substitution during the November defeat against Australia.
That means England coach Andy Robinson might have to field a new midfield combination, and he is understood to be considering handing Jonny Wilkinson the inside centre berth in Cardiff.
Wasps' Stuart Abbott, Leicester's Ollie Smith and Newcastle's Jamie Noon are leading contenders for the outside centre spot if Tindall does not recover in time.