Schalke shocked, Dortmund draw
Hoffenheim picked up their first win in five games as super-sub Sven Schipplock netted the winner just two minutes after coming off the bench to leave the Royal Blues reeling before the Gunners' clash in Gelsenkirchen.
Having won 2-0 in London two weeks ago, Schalke warmed up for the return leg with their first defeat in nine games to rock their confidence.
"We didn't get into the game and we invited the opponent to play football, which they did well," said Schalke coach Huub Stevens. "And if you don't take your chances, like we didn't, then you lose a game which is also what we did."
It had looked as though Schalke had rescued a point after Japan defender Atsuto Uchida had scored a late equaliser for the guests to make it 2-2 on 82 minutes.
Uchida enjoyed a simple tap-in after a cross from Peru forward Jefferson Farfan found Klaas-Jan Huntelaar, who gave his Japanese team-mate the simplest of chances with Hoffenheim goalkeeper Tim Wiese out of position.
But Schipplock hit the winner when played through, drawing Schalke goalkeeper Lars Unnerstall and firing home in the 91st minute.
Brazilian midfielder Roberto Firmino then converted a 67th-minute penalty after Volland was fouled in the box, and it was the 21-year-old who provided the final pass for Schipplock to score the winner. The victory moved Hoffenheim up to 13th while Schalke stay second.
Nurnberg won the battle of the basement teams as midfielder Timo Gebhart scored the winner with a 76th-minute header to move up to 14th and take some of the pressure off coach Dieter Hecking with their first win in seven games.
Hannover are sixth after their 2-0 win at home to Augsburg, while Borussia Monchengladbach were held to a 1-1 draw at their own ground by Freiburg.