The Harlequins flyhalf Demetri Catrakilis was unable to breathe after he sustained a fracture during his side’s victory over Gloucester on Saturday.
The 28-year-old stopped breathing for a few seconds after a shoulder tackle to the throat in the 13th minute of the Premiership fixture.
The flyhalf was taken off the field on a stretcher while receiving oxygen.
"He was struggling to breathe on the pitch, it just wasn’t clearing," John Kingston, the Harlequins director of rugby told the Telegraph.co.uk.
"It alarmed [the medics] which mean he needed to get oxygen and get to the hospital and checked out.
"He’ll probably stay there overnight. He’s in the right place. It’s too early to say it’s precautionary but the bottom line is, when you get a blockage like that’s something you’ve got to react very quickly to,"
According to the Harlequins' injury report posted on Monday, Catrakilis sustained a small fracture to a bone in his throat. He remains in the hospital and does not require surgery.
The South African made his first Harlequins start on Saturday after signing from the French club Montpellier.