Adam Szalai scored in the 85th minute to complete Mainz's amazing comeback from a three-goal deficit to win at Wolfsburg and spoil the Bundesliga return of Brazilian superstar Diego.
Edin Dzeko struck in the 24th and 28th minutes and Diego made it 3-0 after 30 minutes. Morten Rasmussen cut the deficit to 3-1 in the 39th minute, then Elkin Soto struck in the 48th and Andre Schurlle levelled the game at 3-3 in the 58th minute before Szalai's winner.
It was Wolfsburg's second straight defeat to start the season under new boss Steve McClaren.
Werder Bremen picked up their first three points of the Bundesliga season thanks to a Marko Arnautovic-inspired 4-2 win over Cologne. The Austrian striker scored twice and created a third as Bremen enjoyed much the better of a game that saw both sides score after 90 minutes.
Three goals also came in four first-half minutes at the Weser Stadion, the hosts going ahead with a penalty from Torsten Frings in the 33rd minute before Arnautovic doubled their advantage three minutes later.
Lukas Podolski reduced the arrears within 60 seconds, but Bremen were always in control and added two more goals from Hugo Almeida and Arnautovic in the second half. Kevin McKenna grabbed a late consolation for the guests.
Schalke slumped to their second defeat of the season when they lost 2-1 at home to Hanover after another disappointing day for new Spanish signing Raul.
Hanover's Konstantin Rausch fired the visitors into the lead in the 31st minute and Mohammed Abdellaoue doubled it after the restart as Schalke's once mighty defence was rocked.
Jermaine Jones managed to cut the deficit with a well-taken header eight minutes from time but the hosts were unable to find the equaliser and will have to wait longer for their first points this season.
Hamburg scored three times in the final half-hour to beat Eintracht Frankfurt 3-1 and notch their second straight victory to start the season.
Patrick Ochs gave Frankfurt the lead after 37 minutes before Joris Mathijsen levelled the game after 61 minutes and Ruud van Nistelrooy pushed Hamburg ahead in the 81st minute. Paolo Guerrero finished off the scoring in the 89th minute for the visitors.
Papiss Cisse scored twice as Freiburg came from behind to win 2-1 against Nurnberg and register their first victory of the Bundesliga season. The Senegalese striker fired in a penalty just before half-time and headed what proved to be the winner shortly after the break.
Isaac Vorsah's 87th minute goal gave Hoffenheim a narrow 1-0 victory at promoted side St Pauli and first place in the Bundesliga.