Worcester lock Michael Fatialofa has undergone surgery after suffering a neck injury in Saturday's Gallagher Premiership match against Saracens.
The 27-year-old second row was hurt while taking the ball into contact during the 62-5 defeat at Allianz Park.
Play was held up for 15 minutes as he received medical attention and, having been carried from the pitch on a stretcher, he was taken by ambulance to St Mary's Hospital in London.
The operation, aimed at relieving pressure on the Kiwi's spinal cord, was a success and Fatiafola is stable, but he remains in a serious condition and is receiving ongoing care at the Intensive Care Unit of the hospital.
A club statement read: "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.
"Michael and his family are sincerely grateful for the support shown by the rugby community."