Japan's Shinji Kagawa played a starring role as defending champions Borussia Dortmund trimmed Bayern Munich's lead at the top of the German league back to three points with a 4-1 win at Freiburg on Saturday. Ten-man Bayern had opened up a six-point gap with a 3-0 rout of Cologne in Munich on Friday, however second-placed Dortmund enjoyed a comfortable win at Freiburg to stay in touch with the Bavarian giants. Goals by Poland striker Robert Lewandowski, plus Germany midfielders Ilkay Guendogan and Kevin Grosskreutz gave Dortmund a precious victory on the last weekend of the Bundesliga in 2011. Lewandowski claimed his 11th goal of the season after just seven minutes with the simplest of taps after Kagawa had beaten the defence and squared for his team-mate. Freiburg midfielder Jan Rosenthal equalised for the hosts but Dortmund went back in front just before the half-time break when Guendogan fired home for his first goal for the club. By now, the Dortmund attack was in full flow with Kagawa providing some defence-splitting passes as first Lewandowski set up Grosskreutz to slam his shot home. The winger then provided the final pass for the striker to score his second with 20 minutes remaining. Third-placed Schalke have the chance to join Dortmund on 34 points if they beat Werder Bremen on Saturday night. Having drawn defending champions Barcelona in the Champions League Round of 16, Bayer Leverkusen crashed to a 3-0 defeat at home to Nuremberg as their defence left far too many holes for the guests to exploit. Just eight minutes after coming off the bench, Wolfsburg's 20-year-old striker Sebastian Polter netted his first Bundesliga goal on only his second appearance to seal a 1-0 win over Stuttgart. It was only Wolves' fourth win in their last 10 league games. Hoffenheim were held to a 1-1 draw against Hertha Berlin with both sides finishing with 10 men as the guests equalised in added time. Hamburg remain unbeaten under new coach Thorsten Fink after they came from behind to draw 1-1 with Augsburg. Bayern were reduced to 10 men after midfielder Franck Ribery was sent off on 33 minutes after being shown two yellow cards in the space of a minute. But despite the numerical disadvantage, Bayern went ahead after the break when striker Mario Gomez claimed his 16th goal in 16 league games before second-half substitute David Alaba doubled Bayern's lead just after the hour mark. Germany midfielder Toni Kroos then made it three in the dying minutes as unconvincing Cologne's defence fell apart.