Worcester Warriors lock Michael Fatialofa had successful surgery to ease pressure on his spinal cord after being injured in Saturday's match against Saracens.
The operation was necessary because of bruising and swelling, and Worcester said the New Zealander remains "in a serious condition" at St Mary's Hospital in Paddington, London.
Worcester were beaten 62-5 at Allianz Park, with former Hurricanes forward Fatialofa injured and carried off on a stretcher moments after coming off the bench early in the second half.
The Warriors said they are in daily contact with Fatialofa's neurosurgeon and have stressed he has been awake.
A statement from the Premiership club on Tuesday said Fatialofa was "resting and recovering".
"The operation was a success and Michael is stable, but he remains in a serious condition and is receiving ongoing care at the intensive care unit of the hospital," Worcester said.
"The process of recovery and observation of improvement will now begin. As always our thoughts and prayers are with Michael and his family who we will continue support however we can as part of the Warriors family."
Fatialofa's wife Tatiana wrote on Instagram: "@michaelfats strongest man I know. Surgery was a success... but we already knew it would because if God is for us, who can be against us!"