RB Leipzig are the new Bundesliga leaders, for at least 24 hours, after Dani Olmo's goal secured a 1-0 victory away to mid-table VfB Stuttgart as the league resumed in Germany after the winter break.
Leipzig are a point ahead of Bayern Munich but the champions can regain top spot when they host struggling Mainz on Sunday.
Bayer Leverkusen's title hopes took another hit when they again blew a lead, falling to a 2-1 defeat on the road to Eintracht Frankfurt.
Leverkusen lost for the first time this season by the same score to Bayern in their last match of 2020 and they started the new year in similar fashion two weeks later.
In Stuttgart, Olmo converted from close-range after a deflected Angelino cross reached him at the back post midway through the second half. Leipzig had previously missed a host of chances, including a penalty from Emil Forsberg.
Promoted Stuttgart could have snatched a draw only for Waldemar Anton to be denied by visiting keeper Peter Gulacsi in the closing minutes.
"It was a really good night for me, for all the team," Olmo told broadcaster DAZN.
"It's important to start the new year with a win."
Nadiem Amiri opened the scoring for Leverkusen in Frankfurt, but Amin Younes equalised and an own goal from Edmond Tapsoba handed the hosts victory.
"We were chasing the whole game," said Leverkusen coach Peter Bosz.
"No player reached his level, we as a team did not reach our level. Eintracht were better, they had better chances. They deserved the win."
In Berlin, Christian Gross failed to inspire on his debut as new Schalke boss and they suffered a 3-0 defeat to Hertha.
It meant the bottom side are now winless in 30 league games, one short of the all-time record.
Union Berlin meanwhile moved up to fourth thanks to a 2-0 win at Werder Bremen.
In just their second Bundesliga season, Union are flying high after first half goals from Sheraldo Becker and Taiwo Awoniyi put them a remarkable fourth.
Elsewhere, Freiburg continued their good form with a 3-1 win at Hoffenheim.
Borussia Monchengladbach won 1-0 at Arminia Bielefeld thanks to Breel Embolo's goal while Augsburg were 1-0 winners at Cologne thanks to Brazilian Iago's first goal of the season.