Japan winger Shinji Kagawa scored the late winner in Borussia Dortmund\'s 2-1 win over Mainz on Saturday to put the defending champions seven points clear at the top of the German league. This was Dortmund\'s eighth consecutive win to set a new club record. \"After a brief period when we didn\'t play so well, we are now as good as we were last year,\" insisted Dortmund defender Mats Hummels. After second-placed Bayern Munich earlier lost 2-0 at Bayer Leverkusen, Kagawa\'s 77th minute strike capped a fine display after he had also set up Dortmund\'s first goal. The hosts took the lead after Poland captain Jakub Blaszczykowski fired home from Kagawa\'s final pass on 26 minutes. Mainz striker Mohamed Zidan, who only left Dortmund in January, scored in his fifth consecutive game for his new club when he found the net from a tight angle on 74 minutes to beat Dortmund goalkeeper Roman Weidenfeller. \"When they play like this, they are almost impossible to stop,\" said Zidan, who admitted only celebrating quietly against his former club out of respect. Kagawa restored the hosts\' lead when he found space in the Mainz defence just three minutes later.  With 55 points, Dortmund are well clear of Bayern, who are on 48, as Munich\'s poor form continues. Bayern suffered their sixth defeat in the league at Leverkusen while they have won only four of  their last nine games this year. They face a make-or-break few weeks and have to overturn a 1-0 deficit from the first leg of their last-16 tie against FC Basel on March 13 in the Champions League before a German Cup semi-final at Gladbach on March 21. Leverkusen took the lead on 79 minutes when ex-Germany striker Stefan Kiessling tapped the ball home from two yards after Swiss forward Eren Derdiyok\'s overhead kick took Bayern goalkeeper Manuel Neuer out of the game. Midfielder Karim Bellarabi, 21, had been on the pitch just eight minutes when he supported Gonzalo Castro\'s break to slot home Leverkusen\'s second and claim his first goal for Bayer. \"My team demonstrated a great attitude, they really wanted to win and we earned it because of the second-half performance,\" said Leverkusen coach Robin Dutt, whose team face Barcelona in the Champions League on Wednesday. Third-placed Borussia Moenchengladbach can replace Bayern in second place if they win at Nuremberg on Sunday. \"We played really well in the first half and created lots of good scoring chances, which we didn\'t take,\" said Bayern coach Jupp Heynckes.  \"That\'s the crux of our problems at the moment. It was the same for us in Basel. \"It can also happen that the chances go in against you when you don\'t take your own, which is a real pity for my team. \"The result is very disappointing for us all, but we only have ourselves to blame.\" The Bavarians are bidding to avoid a repeat of last season, when they finished in the rare position of having won no silverware. There is also evidence of disharmony in the team as defender Jerome Boateng and midfielder Thomas Mueller engaged in a second-half shouting match. Stuttgart are eighth in the table after they earned a 4-0 win at Hamburg. Hertha Berlin finally broke their seven-match losing streak with a 1-0 win over Werder Bremen as coach Otto Rehhagel, who steered Greece to the Euro 2004 title, enjoyed his first win in only his second game in charge. Schalke\'s ambitions of winning a first Bundesliga title suffered a dent as they fell 2-1 at Freiburg, which lifted  the hosts off the bottom of the table. Kaiserslautern are now bottom of the table after their goalless draw with VfL Wolfsburg, while Augsburg are 16th after their 2-2 draw at Hanover.