Fabian Schar was knocked out after a sickening collision with Eddie Nketiah during Newcastle's 2-0 victory over Arsenal.
It was a night of joy for the Magpies who put a serious dent into their opposition's Champions League hopes after an own goal from Ben White, was followed by Bruno Guimaraes' fifth goal of the season.
However, there was concern for their defender Schar after he collides with Nketiah just seconds into the start of the second-half.
The 30-year-old crashed down heavily on the ground and stayed motionless as the 52,000 seater St James' Park was brought to silence.