Bundesliga club Mainz 05 said Nigerian winger Taiwo Awoniyi, on loan from Liverpool, was taken to hospital for checks after suffering a serious head injury in Sunday's relegation battle at home to Augsburg.
The 22-year-old was briefly motionless after landing awkwardly following a clash of heads with Augsburg defender Felix Uduokhai in the first-half.
Awoniyi was stretchered off with his neck in a brace after a long delay while he received medical attention on the pitch.
Mainz said Awoniyi was responsive and had been taken to hospital for tests.
Awoniyi, who was part of the Nigeria team which won the Under-17 World Cup in 2013, joined Liverpool in 2015.
He has yet to make an appearance for Jurgen Klopp's Reds and has had loan spells at German side FSV Frankfurt, Dutch team NEC and Belgium sides Royal Excel Mouscron and Gent.
With both Augsburg and Mainz just above the relegation places, the visitors took the lead after less than a minute when a volley by Augsburg striker Florian Niederlechner hit the ground and bounced over the Mainz goalkeeper.