Bundesliga leaders Bayern Munich slumped to a 3-1 away defeat at Mainz on Saturday, handing Borussia Dortmund the chance to take top spot.
Dortmund host Eintracht Frankfurt later in the day and can go one point clear with a win, with five league matches remaining this season.
Trailing 1-0 at half-time, thanks to Sadio Mane’s first goal since October, Mainz then hit back scoring three goals through Ludovic Ajorque, Leandro Barreiro and Aaron Martin.
Bayern have now won just two from seven since sacking manager Julian Nagelsmann for former Dortmund and Chelsea boss Thomas Tuchel in late March.
Speaking with German TV after the match, Tuchel said “they gave us a knockout”, saying the side “had too much going on right now to fight back.”
Tuchel said he would give his players three days off ahead of next week’s clash against rock-bottom Hertha Berlin.
“They came out of nowhere, there was no pressing. We didn’t have the energy to react to it, I don’t know why.”
Mainz are now unbeaten in 10 league games and sporting director Martin Schmidt said he was “at a loss for words” to explain his side’s form.
“It’s unbelievable what the team is doing.”
Bayern came into the match under heavy pressure, with the Bundesliga title the last trophy available after Wednesday’s Champions League exit at the hands of Manchester City.
After beginning from the bench against City, Mane and Bayern veteran Thomas Mueller were named in the starting XI by Tuchel.
Mane had the ball in the net after 14 minutes but the effort was chalked off for offside.
Mane, who sat out Bayern’s last Bundesliga match through suspension following an altercation with teammate Leroy Sane, got on the scoresheet shortly after, heading a Joao Cancelo cross past Robin Zentner for the opener after 29 minutes.
Mainz, who were coached by Tuchel between 2009 and 2014, fought back after the break, Ajorque heading in from close range after Yann Sommer failed to grasp a Lee Jae-sung shot.
A shellshocked Bayern, who had controlled the game until that point, looked disorganised and Mainz took advantage by grabbing the lead through Barreiro just eight minutes later.
Martin added another six minutes after that to seal Mainz’s third straight league win over Bayern at home.