RB Leipzig coach Julian Nagelsmann was left ruing the Bundesliga leaders' "sloppy" performance after their first defeat since October as second-half goals by Almamy Toure and Filip Kostic gave Eintracht Frankfurt a shock 2-0 home win on Saturday.
Leipzig's stumble opens the door for defending champions Bayern Munich, who are third, but can cut the gap at the top to just a point if they beat fifth-placed Schalke later at the Allianz Arena.
It was Leipzig's first defeat in 14 games in all competitions since losing 2-1 to Freiburg on October 26 and they are now just two points clear of second-placed Borussia Moenchengladbach.
"We were clearly the better team in the first half, but we were too sloppy with our goalscoring chances," admitted Nagelsmann.
After squandering several clear chances, with Germany striker Timo Werner the main culprit, Leipzig were punished just after half-time.
Frankfurt took the lead against the run of play through right-back Toure's stunning 48th-minute effort.
A throw-in from the left was flicked on to Toure, whose half-volley flew into the top corner with Leipzig goalkeeper Peter Gulacsi at full stretch.
"We defended the throw-in unbelievably badly, we were all over the place afterwards and our game lacked structure," fumed Nagelsmann.
The Leipzig boss reacted to falling behind by taking off midfielders Konrad Laimer and Tyler Adams and bringing on striker Yussuf Poulsen and ex-Everton winger Ademola Lookman.
Leipzig grew ever more desperate in their efforts to equalise and with space opening up, Kostic tucked home Eintracht's second goal in the 94th minute.
Elsewhere in the title race, Moenchengladbach came from behind at home to poach a 3-1 win over Mainz to leapfrog Bayern into second in the table.
After Sweden forward Robin Quaison gave Mainz an early lead, Gladbach's French striker Alassane Plea scored two goals either side of half-time before substitute Florian Neuhaus grabbed a late third.
Jurgen Klinsmann's Hertha Berlin bounced back from their 4-0 thumping at home to Bayern last Sunday, which left them hovering just above the relegation places, with a 2-1 win at Wolfsburg thanks to goals from Dodi Lukebakio and defender Jordan Torunarigha.
Paderborn moved off the bottom of the table with a 2-0 win at Freiburg, thanks to Christopher Antwi-Adjei's goal and a penalty by Abdelhamid Sabiri.
However, the visitors finished with 10 men after left-back Jamilu Collins was sent off with half an hour to go for a second yellow card.
Union Berlin bounced back from their defeat at Leipzig with a 2-0 home win over Augsburg with goals from defender Neven Subotic and Marcus Ingvartsen.
Borussia Dortmund are fourth in the table after routing Cologne 5-1 on Friday with Norwegian teenager Erling Braut Haaland scoring twice off the bench to give him a record five goals in his first two games for the club.