Worcester coach Alan Solomons said Saturday he had "massive concern" over Kiwi lock forward Michael Fatialofa who suffered a serious neck injury in his team's 62-5 English Premiership rout at Saracens.
Auckland-born Fatialofa, 27, came on as a replacement but was hurt after less than a minute of action while taking the ball into contact at the European champions' Allianz Park ground in north-west London.
"For me, a neck injury like that is a massive concern and I am worried about it, but I haven't had any report from the hospital," Solomons said.
"It seemed like he dropped his head as he went into contact, but I haven't studied the footage. It seems like he's taken a blow to the neck.
"The medics have taken all precautions and have done everything possible. We've contacted his partner to let her know."
Play was held up for almost 10 minutes as Fatialofa received medical attention.
He was then stretchered off and taken by ambulance to a London hospital where he was to remain overnight.
"Our thoughts are with Michael Fatialofa. It didn't look great. His health is the most important thing," said Saracens director of rugby Mark McCall.
Fatialofa joined Worcester on a two-year deal in 2018 having helped the Hurricanes to the Super Rugby title in 2016.
In the game itself, Saracens bounced back from their defeat at Exeter to claim a precious bonus-point victory in their pursuit of Premiership survival.
Rooted to the foot of the table after being docked 35 points for breaching salary cap regulations, the champions ran in 10 tries against outclassed opponents.
Rotimi Segun crossed in each half while Ben Earl, Brad Barritt, Mako Vunipola, Richard Barrington, Maro Itoje, Duncan Taylor, Jackson Wray and Elliot Daly also touched down
Meanwhile, Gloucester climbed to third after claiming a bonus-point 29-15 victory over local rivals Bath.
Bath's recent Premiership resurgence came to a grinding halt as they were outscored 4-0 on tries.
Full-back Jason Woodward, flanker Freddie Clarke, number eight Ruan Ackermann and replacement lock Gerbrandt Grobler all scored, with Billy Twelvetrees kicking two conversions and Danny Cipriani one, while Twelvetrees added a late penalty.
Bath relied on five Rhys Priestland penalties for all their points but they lost a three-point advantage when Gloucester hit them with two converted touchdowns in rapid succession midway through the second-half.
Gloucester leapfrogged Sale, who beat Harlequins 48-10 on Friday, into third place.
'Worried': Michael Fatialofa (right) in his Hurricanes days