FRANKFURT, Germany (AP) -- Borussia Dortmund won 1-0 at Hertha Berlin to remain unbeaten in a club-record 16 games and on top of the Bundesliga on Saturday.
Kevin Grosskreutz scored in the 66th minute for the defending champion, which lost to Hertha at home in the first half of the season, but has now won six straight.
Borussia Moenchengladbach also won on the road, beating Kaiserslautern 2-1 to stay in the top three. Bayern Munich can regain second place if it wins at last-place Freiburg in the late match.
Werder Bremen won 3-1 in the northern derby at Hamburger SV, Nuremberg edged Cologne 2-1 and Bayer Leverkusen beat Augsburg 4-1.
In Berlin's Olympic stadium, Dortmund had to play without the injured Japan midfielder Shinji Kagawa and was made to work hard against a team that is winless in 11 games and was playing its 1,000th Bundesliga match.
Shortly before kickoff, Hertha Berlin team manager Michael Preetz confirmed that veteran coach Otto Rehhagel is poised to join the struggling side.
Preetz said the 73-year-old Rehhagel was expected to take over next week. Hertha fired Michael Skibbe a week ago after just five games in charge, all defeats.
Rehhagel "has promised to help us" and will work together with interim coaches Rene Tretschok and Ante Covic until the end of the season, Preetz said. Hertha is two points away from the relegation zone.
Rehhagel led Greece to the European Championship title in 2004, and also coached Bayern Munich, Kaiserslautern and Werder Bremen in the Bundesliga.
He hasn't worked since resigning as Greek coach in 2010. His last stint in the Bundesliga ended in 2000 with Kaiserslautern, which he sensationally coached to the title in 1998 having led the side to promotion the year before.
Striker Lucas Barrios started in Kagawa's place, with Robert Lewandowski playing a more midfield role.
Dortmund's midfield labored without Kagawa, but Lewandowski played a part in creating Dortmund's goal.
He connected with a cross from Jakub Blaszczykowski, Hertha's goalkeeper Thomas Kraft parried his header but Grosskreutz reacted with an overhead volley into the roof of the net.
"It was a hard-earned win," Dortmund's goalkeeper Roman Weidenfeller said. "We had a couple of chances in the first half but it was close and we showed good morale."
Moenchengladbach won for the first time since 1995 in Kaiserslautern, getting early goals from Patrick Herrmann and Juan Arango.
Herrmann finished a counterattack in the ninth off a pass from Igor de Camargo and Arango scored a spectacular goal five minutes later, after Pirre de Wit had hit the crossbar of Moenchengladbach's goal.
Marco Reus sent a perfectly timed pass behind three Kaiserslautern defenders and scored with a first-touch shot with the outside of his left foot inside the far post.
Leon Jessen also scored a fine goal in the 63rd to cut Kaiserslautern's deficit but the home side could not find the equalizer.
Herrmann was carried off the field in the first half and the club later said one of its top players had suffered a broken collarbone.
"It was very, very difficult but it was an important win," Moenchengladbach coach Lucien Favre said.
Bremen snapped a four-game run of draws by winning the highly charged match in Hamburg.
Marko Marin opened the scoring in the ninth and Tom Trybull headed in off a corner with the last shot of the first half to double the lead.
A deflected free kick from Mladen Petric put Hamburg back into the match but Marko Arnautovic secured Bremen's win in the 86th. Heiko Westermann and Slobodan Rajkovic failed to agree who would clear a long kick from goalkeeper Tom Wiese and Arnautovic took advantage of their confusion to collect the ball and score from close range.