Japan midfielder Shinji Kagawa and Paraguay forward Lucas Barrios score in second half . Hide Caption Second-placed Mainz will try to reduce the deficit in Saturday 's home clash with Hannover . Defending champions Bayern Munich 15 points adrift ahead of Sunday 's match .
Japan midfielder Shinji Kagawa and Paraguay forward Lucas Barrios score in second half . Dortmund unbeaten since opening day of the season , with 10 wins from 12 games . Second-placed Mainz will try to reduce the deficit in Saturday 's home clash with Hannover . Defending champions Bayern Munich 15 points adrift ahead of Sunday 's match .