Sale Sharks prop Andrew Sheridan could miss England's three November internationals after dislocating his left shoulder in his side's 27-26 win over Cardiff Blues.
The British & Irish loose head specialist had to have his shoulder put back into place in the dressing room after suffering the dislocation at a 73rd minute scrum.
Ironically, the injury came at a scrum at which the Blues tight head prop, Tongan international Fa'ao Filise was penalised for collapsing. But while he trotted away, Sheridan was left in a heap on the ground.
He received medical attention on the pitch for almost five minutes before being led away with his left arm outstretched.
It took three attempts by the doctor to put in back into place and he will undergo scans on the joint on Saturday afternoon.
Sheridan's Lions team mate Adam Jones suffered a similar dislocation in the second| test in South Africa in the summer and was forced to undergo surgery that is set to keep him out of action until the new year.
"Andrew was in a lot of pain in the dressing room and it is distressing seeing a player in that position," said Sale Sharks director of rugby Kingsley Jones.
"He has never had an injury like that to his shoulder and it is too early to guess at how long he will be out for. He will see the specialist over the weekend and we'll take it from there."
England are due to play Australia, Argentina and New Zealand in November and it would be a huge blow to Martin Johnson's plans if Sheridan were ruled out.
Jones is also hoping that the injury won't keep Sheridan out of the back-to-back Heineken Cup clashes with Harlequins in December. Having got their European campaign back on track with the win over the Blues, Jones is hoping his side can pick up more points in those two games.