Hill's career on line over injury

The 32-year-old underwent surgery on 9 July but returned to hospital for two weeks after feeling unwell.

"It's a huge blow for Richard and the club," said Saracens director of rugby Steve Diamond.

"He'll probably be out for eight months, so he could return at the back end of the season if all goes to plan."

Hill, who was sidelined from last October to April after surgery on the same knee, suffered the injury early in the first Lions Test against New Zealand.

Former Great Britain rugby league captain Andy Farrell has joined the club and had been mentioned as a possible back-row replacement for Hill.

Convert Farrell wins England call

But Farrell, included in England coach Andy Robinson's initial elite training squad, is likely to begin his union career in the backs at inside centre.

"We have a clear picture of the role Andy is going to play for us," said Diamond, who moved to the director of rugby role after a restructuring of Saracens' coaching team.

Ireland defensive coach Mike Ford will take on the role of head coach.

We're looking for two more players to join the squad Saracens director of rugby Steve Diamond

"His distribution skills and understanding of where he is on the field are such that he will be a major decision maker for us.

"We won't hide from the fact he'll play at inside centre or in the back row, but primarily we're looking at inside centre to begin with.

"We'll start him there and see how he does. He's very versatile and we're looking at things pragmatically."

All Blacks and Waikato flanker Marty Holah seems a more probable replacement for Hill, with the 28-year-old out of contract at the end of the year.

Diamond said Saracens were in the market for southern hemisphere players, without naming his intended targets.

"We've got a fair stack in our salary cap at the moment and we're looking for two more players to join the squad," said Diamond.

"If one or two from the southern hemisphere come up after the Tri-Nations or at the end of their seasons then we've got the wherewithal to purchase those people."

Waikato chief executive Gary Dawson has admitted Holah may be on the verge of leaving the province.