Mainz now have the upper hand in the Bundesliga relegation fight after they cruised to a 3-0 victory against Champions League finalists Borussia Dortmund, who rested several starters. With 32 points, Mainz are no longer in danger of automatic relegation and will remain in the Bundesliga if they defeat VfL Wolfsburg next weekend. Other results could lead to a relegation play-off against the third-placed in the second division. The hosts took the lead in the 12th minute from Leandro Barreiro’s side-foot finish. Jae-sung Lee made it 2-0 just six minutes later before he completed a brace in the 23…