England and Sale Sharks centre Manu Tuilagi is set to be out for at least six weeks after he injured his hamstring while on international duty.
Tuilagi will now see a specialist to confirm the next steps and extent of the lay-off.
“I’m really gutted,” Sharks boss Alex Sanderson said.
“I’m gutted for him and gutted because we were managing him well and then something like that happens.”
The Samoa-born former Leicester three-quarter has struggled with hamstring, knee and Achilles problems at various stages during his career.
He once missed 15 months while at Tigers with a groin injury, before returning in January 2016.
England begin their Six Nations campaign with the Calcutta Cup match against Scotland at Murrayfield on Saturday, 5 February.