England captain Jonny Wilkinson has suffered another setback after being taken off injured during Newcastle's 23-39 loss against Harlequins.
Wilkinson left the field on 34 minutes at The Stoop after injuring the same left knee that has kept him out of action for the last two months.
The Falcons fly-half had kicked two penalties and a conversion before being injured trying to tackle Ceri Jones.
He will undergo a scan on Monday to assess the extent of the injury.
Mar 2005: Injures knee in comeback game against Harlequins
Jan 2005: Suffers medial ligament damage against Perpignan
Dec 2004: Returns as substitute against Edinburgh in Heineken Cup
Oct 2004: Ruled out of autumn Test programme due to a haematoma in the upper right arm.
Aug 2004: Makes comeback in Newcastle's pre-season friendly against Connacht
Feb 2004: Told that he needs an operation on shoulder
Dec 2003: Learns that he has a fractured facet in his shoulder
He took his place on the bench when he came off but at half-time had to be helped to the changing rooms.
Wilkinson was not originally named in the starting line-up for the game but came into the side after Joe Shaw's late withdrawl and Dave Walder's switch to full-back to cover.
But Newcastle's director of rugby Rob Andrew told the BBC Wilkinson was ready to return.
"He would not have started unless he was totally happy," Andrew said. "Jonny has had a fantastic week. The medical team were very happy and there was no issue.
"He has worked really hard in the last nine weeks, was fantastic last week in training and, for the 30 minutes he was on the field, it never looked as though he had been away.
"He has just gone into a tackle and twisted his knee - it's the same knee no doubt about that - and that has caused a problem.
"Of course he is disappointed and frustrated - it's the same for everyone involved with him."
But Andrew said he was unwilling to speculate on the seriousness of the injury and the length of lay-off the kicker could face.
"Until we have had the scan and they can clinically have a look at him closely, it is pointless me speculating," he said.
"It could be nothing and he could be back in two weeks' time, or he could be facing another lengthy rest - we just don't know."
Wilkinson's setback is the latest in a long line of injuries he has suffered since the 2003 World Cup final.
He has not played international rugby since kicking the winning drop goal for England on that dramatic night in Sydney.
And he could be a major doubt for the British and Irish Lions tour to New Zealand this summer.