A second-half header from defender Paul Jaeckel helped Union Berlin go two points clear at the top of the Bundesliga table with a hard-fought 1-0 win at 10-man Stuttgart on Sunday.
Jaeckel's 76th-minute goal was followed by a second yellow card for Serhou Guirassy just seven minutes later, leaving Stuttgart short-handed and Union in control.
Union's rivals Freiburg, Bayern Munich and Borussia Dortmund all drew this weekend, giving the Berliners a chance to extend their lead.
Stuttgart-born Union midfielder Rani Khedira said relief rather than elation was the major feeling.
"It was a lucky win for us. We wanted to play compact and then somehow score the goal," Khedira told DAZN.
"We managed to do that. We didn't show a nice game -- you could tell we were tired."
Union coach Urs Fischer agreed with Khedira, saying "given the chances, you might need a bit of match luck -- and we had that today."
"We were a bit sloppy in the beginning, but over time we got better and better -- the boys did a great game today."
Union has now been on top of the table for four consecutive weeks but the current two-point gap is the widest so far.
Stuttgart is second-to-last and the only team in the Bundesliga without a win this season.
Stuttgart's American coach, Pellegrino Matarazzo, said he understood the boos coming from the home fans at full time, but felt his side was making progress.
"The chances we had against Union, I feel not many teams have those chances -- but we have to do something with those chances."
Earlier on Sunday, Freiburg missed a chance to stay level with Union, drawing 2-2 away at Hertha Berlin in the absence of Covid-hit coach Christian Streich.
Stand-in Lars Vossler said after the game he was "happy with a point" -- Freiburg's third draw in its past four games -- after a "complicated" match.
Freiburg's Daniel-Kofi Kyereh opened the scoring after 22 minutes, set up by Japanese winger Ritsu Doan. Hertha struck back just 10 minutes later, when Dodi Lukebakio converted a penalty. Suat Serdar scored a superb solo goal in the 61st minute to give Hertha the lead.
With the home side seemingly on track for what would have been just their second win of the season, substitute Kevin Schade scored in the 78th minute, pouncing on a free-kick fumbled by goalkeeper Oliver Christensen.
Hertha coach Sandro Schwarz, whose side has now not lost since late August, said the failure to win was "annoying."
"We've put a lot of effort in over the past few weeks, so it was difficult to accept that again we were unable to win," he said.
Hertha has won just once and drawn five times from nine games this season.
Ramy Bensebaini scored twice as Borussia Moenchengladbach thrashed 10-man Cologne in the Rhine derby 5-2 at home.
Cologne saw Florian Kainz, who had earlier scored a penalty, sent off in first-half stoppage time after conceding a spot-kick and picking up a second yellow card.
Bensebaini, an Algeria international, converted from the spot to give Gladbach, which had struck first through Marvin Friedrich, a 2-1 lead. Lars Stindl made it 3-1 with a goal just after halftime, while Bensebaini added one from open play after 76 minutes to put the result beyond doubt.
Cologne's Denis Huseinbasic gave his team a glimmer of hope in the 83rd minute, but France striker Marcus Thuram struck in stoppage time to wrap up the win for Gladbach.
Gladbach, which was thumped 5-1 by Werder Bremen last weekend, climbed up the tightly packed Bundesliga standings to sixth -- one point behind Bayern Munich and Borussia Dortmund, which drew 2-2 on Saturday.
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