United States international Weston McKennie scored his first Bundesliga goal in Schalke's 2-0 win over Fortuna Dusseldorf on Saturday before leaving the game with an apparent injury.
It was the second goal in as many games for McKennie, who has been called up for friendlies against Colombia and Peru next week.
McKennie, 20, made way for Yevhen Konoplyanka in the 79th minute with what Westdeutsche Allgemeine Zeitung reported was a bruised left calf, but coach Dominico Tedesco said the midfielder was merely exhausted.
"It's a very good sign when players like [McKennie] are so tired at the end of games," Tedesco said at a news conference. "The first goal was very important for our confidence."
McKennie opened the scoring for Schalke in the 47th minute with a right-footed volley from close range after Suat Serdar's header following a corner.
The goal came three days after McKennie scored his first goal for Schalke in the 1-0 victory over Lokomotiv Moscow in the Champions League.
Meanwhile, U.S. teammate Bobby Wood scored his first two goals for Hannover in a 3-1 home win against Stuttgart.
Wood, who joined Hannover on loan from Hamburg in the summer, scored twice from a header in the first half, opening the scoring in the 30th minute and doubling the lead just before the break.
He nearly completed the hat trick in the 75th minute, with a third header saved by Ron-Robert Zeiler before coming off in the 76th minute.