The Schalke team-mates were passengers in cars driven by Nico Rosberg and his fellow race car driver Pascal Wehrlein.
Julian Draxler and Benedikt Howedes escaped unhurt after a crash involving cars being driven by F1 driver Nico Rosberg and his fellow racer Pascal Wehrlein.
Two people had to be taken to hospital when a car driven by Wehrlein crashed into them, with one person in a serious condition.
The accident occurred close to the German team's base in South Tyrol, northern Italy, with Wehrlein and Rosberg doing laps of a short circuit in the mountains.
German football federation spokesman Jens Grittner said: "A driving exercise of our partner Mercedes-Benz ended in a serious accident. To our great regret, two people were injured. They were treated immediately and brought to hospital."
