The flanker was helped off clutching his left knee in the 39th minute of the Premiership clash at Reading.

Saracens are refusing to comment about the extent of the injury until it is assessed when Hill reports for an England training session.

But coach Rod Kafer admitted: I'm very worried about what Richard Hill's injury means to the team in both the short-term and the long-term.

Hill, 31, is England's most experienced flanker with 71 caps and a World Cup winners medal to show from his long career, and was the only man sure of his place in the England back row for this autumn's three Twickenham internationals.

The back row cupboard looks increasingly bare now Lawrence Dallaglio and Neil Back have retired, while Leicester's Neil Moody is this week beginning his comeback from a long-term foot injury.

And the loss of Hill would be a major blow to acting England boss Andy Robinson as he prepares for Tests against Canada, South Africa and Australia.