Mainz recovered from three goals down to shock Wolfsburg 4-3 on Saturday and spoil the Bundesliga return of Brazilian superstar Diego.
After Edin Dzeko's double, Diego put Steve McClaren's Wolfsburg side 3-0 ahead after half an hour, but Adam Szalai completed a remarkable recovery with the winner for Mainz in the 85th minute.
Schalke's dismal start to the season continued with a 2-1 home defeat by Hannover, but Werder Bremen bounced back from an opening day loss with a 4-2 win over Cologne.
Diego only signed for 2009 league champion Wolfsburg from Juventus on Friday, but he proved to be a real handful for Mainz.
Dzeko struck in the 24th and 28th minutes before Diego got on the scoresheet himself, with Wolfsburg seemingly cruising.
But Mainz stormed back into the game with Morten Rasmussen (39th), Elkin Soto (48th) and Andre Schuerlle (58th) scoring to tie the game, before Szalai finished off Wolfsburg in the 85th to give Mainz six points from two rounds.
"We just kept believing in ourselves," said Mainz coach Thomas Tuchel, whose team improved to six points. "We had not played badly until then. And Wolfsburg were only dangerous on the counter attack."
Wolfsburg coach McClaren has tasted defeat in his first two games in the Bundesliga after arriving from Dutch side FC Twente in the offseason.
"I've been in football for more than 35 years and I cannot remember losing a game that we led 3-0. It's a new feeling that we all have to swallow," said Wolfsburg general manager Dieter Hoeness. "It may take a while, but we have to get past this one."
Hamburg also have six points after a 3-1 victory at Eintracht Frankfurt.
After going behind, Ze Roberto corners were headed in by Joris Mathijsen (61st) and Ruud van Nistelrooy (81st) before Paulo Guerrero ended all doubts in the 89th minute.
"We are all happy that we have two victories in two games," said Van Nistelrooy, who has scored three goals so far. "But we cannot get too excited. We have only played two games.
Hannover notched its first victory at Schalke in seven years by winning 2-1, pushing Felix Magath's side even further into turmoil.
Konstantin Rausch and Mohammed Abdellaoue gave Hannover a 2-0 lead and the visitors held on for the win.
"This is not the start that we had hoped for," said Magath, whose team has zero points from two matches. "But we have time to work on finding ourselves and we need to do that.
"We lost some confidence after the mistake for the 1-0 deficit. The situation kind of confused us. This is not the start that we had hoped for, but we have time to work on finding ourselves. And I am certain that all our problems can be solved."
Marko Arnautovic scored two goals and set up a third in Werder Bremen's convincing 4-2 victory at home over Cologne.
Papiss Cisse scored two goals as Freiburg came back to beat Nuremberg 2-1 on the road.
Promoted side St. Pauli was hosting Hoffenheim later Saturday.
On Friday, promoted Kaiserslautern upset reigning champion Bayern Munich 2-0. And on Sunday Bayer Leverkusen welcomes Borussia Moenchengladbach and Stuttgart hosts Borussia Dortmund.
