Borussia Dortmund striker Michy Batshuayi was carried off on a stretcher with a possible ankle injury as they lost the Ruhr valley derby to Champions League rivals Schalke.
The Belgium forward, on loan from Chelsea, was caught by a Benjamin Stambouli tackle in the closing stages and had to come off.
Yevhen Konoplyanka scored the opening goal after a Marcel Schmelzer error.
And Naldo drove in from 25 yards after a short free-kick to secure the win.
Dortmund boss Peter Stoger said of Batshuayi’s injury: “I didn’t think it looked like the kind of injury that he would be back from quickly.
“I hope, of course, that I’m mistaken. I can’t yet say anything specific, other than the fact that he’s in pain and will now be examined in more detail. Hopefully, it’s not as bad as it looks.”
Schalke remains second but are now four points above fourth-placed Dortmund.
Later on Sunday, England Under-21 winger Ademola Lookman, on loan from Everton, scored his second RB Leipzig goal as they drew 1-1 with Werder Bremen.