Union Berlin climbed level on points with Bayern Munich at the top of the Bundesliga on Saturday, with a 2-0 away win at derby rivals Hertha Berlin.
Bayern can pull ahead again later Saturday when they host Eintracht Frankfurt.
Union took the lead late in the first half through Dutch defender Danilho Doekhi, who headed in a free-kick from captain Christopher Trimmel.
Union doubled their lead halfway through the second half through midfielder Paul Seguin to run out victors over a spirited but toothless Hertha.
Visiting fans began singing "city champions" with 10 minutes remaining, celebrating their fifth consecutive derby win.
Union's win sees them sit an unlikely second on goal difference behind the league leaders, while deepening the woes of Hertha, who are second bottom having won just three games all season.
After the match, Union coach Urs Fischer sought to play down expectations, telling AFP's sports subsidiary SID that his side "did not look like a top team".
"It was a hard-fought derby. It was close over 90 minutes. In the end, we were lucky winners. We were efficient," he said.
Elsewhere, Freiburg beat Augsburg 3-1 at home to move into fourth place.
First-half goals by towering Austrian striker Michael Gregoritsch and fellow forward Lucas Hoeler put Freiburg in the driving seat.
A 29th-minute penalty from Mergim Berisha gave the visitors hope, but Freiburg sealed their first win of 2023 through an 85th-minute strike from Philipp Lienhart.
In Bremen, Germany striker Niclas Fuellkrug scored both his side's goals in a 2-1 win over Wolfsburg, overcoming RB Leipzig forward Christopher Nkunku to top the Bundesliga scoring charts with 13 goals this season.
Promoted Bremen, who had lost six of their past eight matches came up against an in-form Wolfsburg who were unbeaten in 11 matches under former Bayern coach Niko Kovac.
Borussia Moenchengladbach deepened Hoffenheim's woes with a 4-1 away win.
Two first-half goals and a second-half assist for captain Lars Stindl from midfielder Jonas Hofmann, Gladbach's only representative in Germany's 2022 World Cup squad, gave the visitors a comfortable victory.
The win sentenced Hoffenheim to their sixth defeat in their last nine games, leaving them just three points clear of the relegation playoff spot.
Mainz overcame the disappointment of Wednesday's last-gasp loss to Borussia Dortmund, thrashing Bochum 5-2 at home, their first win in six league matches dating back to October.
A hat-trick from Austrian forward Karim Onisiwo, plus goals by Lee Jae-sung and Silvan Widmer lifted Mainz into 11th ahead of a midweek German Cup meeting at home with Bayern.