Schalke remain third in the Bundesliga with a 2-1 away victory over Borussia Dortmund in the Revierderby.
The first chance of the game fell to the German champions in the sixth minute, when Marco Reus's free kick across the face of the goal went to Sebastian Kehl, but the midfielder failed to take his chance.
That miss came to haunt Dortmund eight minutes later when Ibrahim Afellay volleyed home off the post to give Schalke the lead.
Reus created the best chance of the first half for BVB at Signal-Iduna-Park on 37 minutes, when he shot at goal, but Unnerstall made a comfortable save. Minutes later Robert Lewandowski spurned his chance.
Lewandowski, though, halved the deficit on 55 minutes, as he flicked Reus's free kick into the visitors' goal to bring Dortmund back into the game.
Afellay came close to making it 3-1 to Schalke on 71 minutes when he made a fierce attempt on the Dortmund goal, but was denied by Roman Weidenfeller.
The defeat leaves Dortmund 12 points behind leaders Bayern Munich.