Demetri Catrakilis was taken to hospital after he stopped breathing for several seconds during his side’s Premiership victory over Gloucester.
The Harlequins fly-half was injured by a shoulder hitting him near his throat minutes after he had kicked the first penalty of the Twickenham Stoop contest as Quins went on to win 28-17.
Harlequins director of rugby John Kingston explained afterwards: “He has gone to hospital. He was struggling to breathe on the pitch. The area to breathe properly was not clearing which needed to get oxygen.
We needed to get him to hospital. They will probably assess him overnight. It is precautionary but when you get a blockage like that, it is something you have to react quickly to.
“It was a shoulder to his throat. That was causing him difficulty and, indeed, he did not breathe for a few seconds.
“But then he started to and the oxygen helped him after he came off the pitch.”