Champions Bayern Munich crashed to a 3-2 loss at VfL Bochum on Sunday for a third straight defeat in all competitions that saw them drop eight points behind Bundesliga leaders Bayer Leverkusen.
The Bavarians, who had Dayot Upamecano sent off for the second consecutive match after his dismissal in Wednesday's Champions League loss to Lazio, earned a 13th-minute lead with Jamal Musiala drilling in from a tight angle.
But Bochum struck twice before the break with Takuma Asano and Keven Schlotterbeck to complete a stunning comeback for the hosts and pile more pressure on embattled Bayern coach Thomas Tuchel.
The game was repeatedly interrupted, with fans throwing tennis balls on to the pitch in protest at a planned foreign investment in the Bundesliga.
The hosts added a third with an 85th-minute Kevin Stoeger penalty after Upamecano's dismissal for elbowing an opponent in the box. Harry Kane cut the deficit with a tap-in in stoppage time for his 25th league goal.
Bayern are in second place on 50 points, eight behind Leverkusen, while Bochum moved up to 11th on 25.
World number two Iga Swiatek advanced to the second round of the Australian Open on Monday with an unconvincing 6-3 6-4 win against first-time opponent Katerina Siniakova on John Cain Arena.
Jannik Sinner launched his Australian Open title defence with a 7-6 7-6 6-1 win over Nicolas Jarry on Monday in a match that put the players' contrasting doping cases in the spotlight, while Carlos Alcaraz began his bid to complete a career Grand Slam with a 6-1 7-5 6-1 win over Kazakh Alexander Shevchenko.
Manchester United boss Ruben Amorim said his team are still improving, as Sunday's dramatic FA Cup penalty shootout victory over Arsenal points to a more positive future after a difficult start to life at Old Trafford.