Bayern Munich missed their first chance to confirm a record-extending ninth consecutive Bundesliga title on Saturday when they slumped to a 2-1 defeat at Mainz in a miserable performance.
A terrible error from goalkeeper Manuel Neuer gifted Jonathan Burkardt a third minute opener and Robin Quaison doubled Mainz's lead before half-time.
The on-form hosts missed plenty other chances to score but - unlike when they lost 5-2 in Munich after leading Bayern 2-0 at half-time earlier in the season - were not punished.
Bayern struggled with even fit-again star Robert Lewandowski unusually slack in front of goal, though he did net his 36th of the season with an injury-time consolation.
Topping the table by 10 points, Bayern could yet be crowned champions this weekend if second-placed RB Leipzig lose at home to VfB Stuttgart on Sunday.
Fifth-placed Borussia Dortmund's closed in on the Champions League with a crucial 2-0 win at Wolfsburg despite Jude Bellingham's red card. Erling Haaland's double moved them within two points of Wolfsburg in third while Eintracht Frankfurt, fourth, visit Bayer Leverkusen in the late game.
Joel Pohjanpalo's hat-trick kept Union Berlin's European dream on track with a 3-1 win over relegation-threatened Werder Bremen, who have lost seven in a row.
Midtable Hoffenheim drew 1-1 at Freiburg in the other game.
