Worcester's Michael Fatialofa will remain in hospital on Sunday evening after suffering a neck injury against Saracens on Saturday.
The 27-year-old was hurt in a collision just a minute after coming on, with play halted for 15 minutes as the lock received medical attention before being carried from the pitch on a stretcher.
Fatialofa was taken by ambulance to St Mary's Hospital in Paddington and will now be kept under watch for a second night.
"On behalf of Michael we would like to thank all those who have passed on messages of support and concern," read a statement on Worcester's website.
Warriors director of rugby Alan Solomons said in his post-match press conference: "It seemed like he dropped his head as he went into contact.
"I haven't studied the footage but it seems like he's taken a blow to the neck.
"For me, a neck injury like that is a massive concern and I am worried about it, but the medics have taken all precautions and have done everything possible."
