Berlin: German league runners-up Bayer Leverkusen started the new season with a 2-0 defeat at Mainz 05 on Sunday thanks mainly to two mistakes in the Leverkusen defence.
A first-half blunder by stand-in goalkeeper Fabian Giefer and a late own-goal from defender Omer Toprak gifted the hosts the three points and last season`s runners-up were left nursing defeat after last week`s shock cup exit.
Mainz took the lead on 32 minutes after defender Stefan Reinartz back-passed to Leverkusen goalkeeper Giefer who completely mistimed his clearance kick and the ball rolled out of his control.
It turned into a foot race between him and Mainz striker Sami Allagui which the Tunisia international won and smashed his shot home from a tight angle.
Bayer coach Robin Dutt had dropped American goalkeeper David Yelldell in favour of Giefer after Leverkusen`s shock 4-3 German Cup defeat at Dynamo Dresden the week before with first-choice Rene Adler out with a knee injury.
Mainz made sure of the points when Toprak`s sliding tackle led to the ball rolling past the despairing Giefer and into the empty net on 86 minutes.
Title holders Borussia Dortmund had started proceedings on the opening weekend of the season with an impressive 3-1 win over Hamburg on Friday thanks to two goals from Germany`s rising stars Kevin Grosskreutz and Mario Goetze.
On Saturday, former Bundesliga champions VfB Stuttgart and VfL Wolfsburg picked up wins to go top of the table.
Germany`s Brazil-born striker Cacau warmed-up for Wednesday`s friendly against the South Americans in Stuttgart with a 37th-minute goal as 2007 German champions VfB Stuttgart enjoyed a 3-0 win over Schalke.
The hosts added a second when Austria striker Martin Harnik scored with a 56th-minute header before Japan striker Shinji Okazaki came off the bench to score with a superb strike in the 89th minute.
Patrick Helmes scored twice as 2009 champions Wolfsburg won 3-0 at Cologne.
Hanover 96, who face Sevilla in a Europa League play-off on August 18, were also winners with a 2-1 victory over Hoffenheim.
Having spent last season flirting with relegation, Bremen got their season off to a flying start with a 2-0 home win over Kaiserslautern as Sweden striker Markus Rosenberg netted twice in the second half.
Striker Sascha Moelders scored with two headers as newly-promoted Augsburg earned a 2-2 draw at home to Freiburg.
Hertha Berlin, back in the Bundesliga after winning the second division last season, were beaten 1-0 at Berlin`s Olympic Stadium on Saturday night after Nuremberg`s 22-year-old Czech Republic striker Tomas Pekhart netted the winner.
Bayern Munich open their season on Sunday evening at home to Borussia Moenchengladbach.