BERLIN (AP) -Defending champion Borussia Dortmund slumped to a 2-1 loss at home to bitter rival Schalke in the 141st Ruhr derby on Saturday, while Bayern Munich became the first side to start the Bundesliga with eight wins.
"We didn't play well, that was the first problem," said Dortmund coach Juergen Klopp.
Ibrahim Afellay opened the scoring in the 14th minute, when he crashed a low shot in off the left post, and Schalke went 2-0 up in the 48th, when Marco Hoeger finished off a counterattack after a brilliant through ball from Lewis Holtby.
Robert Lewandowski pulled one back with a header from Marco Reus' free kick seven minutes later, but it wasn't enough to save Dortmund's 17-game unbeaten run at home or prevent the side falling 12 points behind Bayern.
"We didn't play enough football," Klopp said. "Altogether it was a deserved win for Schalke."
Thomas Mueller scored twice in Bayern's 5-0 rout of Fortuna Duesseldorf, with Mario Mandzukic, Luiz Gustavo and Rafinha also on target for the visitors.
Elsewhere, Freiburg won 2-0 at Wolfsburg, Bayer Leverkusen drew 2-2 with Mainz, and second-place Eintracht Frankfurt beat Hannover 3-1.
Marco Arnautovic scored one and set up another as Werder Bremen enjoyed a comfortable 4-0 win over Borussia Moenchengladbach.
"We forget to defend sometimes, and we're paying the price," said Moenchengladbach coach Lucien Favre.
Nils Petersen opened the scoring in the 37th, before Arnautovic made it 2-0 at the interval with a delicate chip over the outrushing Marc-Andre ter Stegen.
Arnautovic eluded two defenders to set up substitute Niclas Fuellkrug in the 76th, before Zlatko Junuzovic completed the scoring by stopping the ball with the back of his heel and hitting it on the half-volley beyond the helpless Ter Stegen.
"It's important for the forwards. That's why they're there - to score goals," said Bremen captain Aaron Hunt, who split the defense for Arnautovic's first.
The Ruhr derby was overshadowed by serious rioting outside Dortmund's stadium before kickoff. The dapd news agency reported that at least 150 fans were arrested, and that police used a water cannon and pepper spray to bring the situation under control. Some 600 Schalke fans were prevented from clashing with several hundred Dortmund supporters. Local police had 1,000 officers on duty for the high-risk game.
Dortmund, which hosts Real Madrid in the Champions League on Wednesday, started without four injured internationals - Mario Goetze, Jakub Blaszczykowski, Marcel Schmelzer and Ilkay Guendogan - and Klopp amended his formation with three at the back.
"We were a bit surprised that Dortmund played with a different formation. But we adjusted to it," said Schalke coach Huub Stevens, who was missing Greek defender Kyriakos Papadopoulos and German midfielder Julian Draxler for the club's 1,500th Bundesliga game.
"We fought very well (after Dortmund scored) and deserved to bring home the win," Stevens said.
Schalke has concerns over Holtby's fitness ahead of Wednesday's visit to Arsenal after the forward went off after a hard but fair challenge from Neven Subotic.
In Duesseldorf, Franck Ribery delivered a perfect cross for Mandzukic's seventh goal of the season in the 28th, eight minutes before Luiz Gustavo inadvertently scored Bayern's second.
Ribery was again involved when Mueller made it 3-0 in the 55th, David Alaba crossed for the Germany international's second in the 86th, and Rafinha rounded off the scoring a minute later.
"We really wanted to win this game," Bayern coach Jupp Heynckes said. "What impressed me most of all was that we allowed absolutely nothing at the back."
Gonzalo Castro's 87th-minute equalizer salvaged a point for Leverkusen, following goals from Adam Szalai and former Leverkusen player Marcel Risse for Mainz. Stefan Kiessling had given Leverkusen the lead in the 43rd.
Wolfsburg was bottom of the table after a Daniel Caligiuri penalty and Julian Schuster strike condemned Felix Magath's side to its fifth defeat of the season.
"We had big plans to put them under pressure," Magath said. "We didn't do it."
The under-pressure Magath will come under further scrutiny after opting to leave Brazilian playmaker Diego on the bench.
"When we saw the lineup without Diego, we knew to expect a lot of high balls. Our defense dealt with it well," said Freiburg coach Christian Streich.
Frankfurt made a blistering start against Hannover, with Karim Matmour and Sebastian Jung making it 2-0 by the 18th minute.
Mohammed Abdellaoue pulled one back in the 43rd, but Alexander Meier sealed the win in the 83rd.
"I'm rather proud that my team won against such a good side," said Frankfurt coach Armin Veh.