Dortmund warms up with Mainz win
Marco Reus and Robert Lewandowski, who scored for the 12th game in a row, earned Jurgen Klopp's men all three points in a game they dominated, yet almost threw away in the second half.
Mainz arrived with a weakened side due to injuries and, despite a valiant attempt, were unable to return with anything tangible for their efforts.
Reus gave Dortmund a flying start with a goal after just 33 seconds.
The Germany international scored into an open goal after Christian Wetklo made a hash of Mats Hummels' long ball forwards.
Dortmund continued to attack with Reus denied by Wetklo, who showed quick reactions also to prevent Neven Subotic from scoring a second for the home side.
Lewandowski, seeking to score for the 12th game in a row, thought he had done that in the 29th minute when he put the ball past Wetklo, but the offside flag was raised and the goal did not count.
Marcel Schmelzer went close twice and Reus could have added a second as Dortmund tried to finish Mainz off as soon as possible to enable them to focus on their Champions League tie with Real Madrid on Wednesday.
Former Real forward Adam Szalai gave the Westphalians something to think about in the 73rd minute as Mainz threatened an equalizer.
But Lewandowski got the goal which keeps him on course to catch Gerd Muller's record of scoring in 16 consecutive games with a 90th-minute goal securing all three points.
Meanwhile in Spain, Mesut Ozil scored twice in Real Madrid's 3-1 win over Real Betis on Saturday as the Spanish side warmed up for its Champions League semifinal against Borussia Dortmund.
Karim Benzema passed for Oezil to net Madrid's opener in the 45th minute before the France striker polished off a counterattack in the 57th.
Oezil struck again in stoppage time after Betis substitute Jorge Molina pulled one back with a penalty kick in the 72nd following defender Nacho Fernandez's foul of Ruben Castro in the area.
Madrid's Spanish league victory came at a cost, however, with Marcelo and Luka Modric both needing to be substituted for injuries.
Madrid visits Dortmund on Wednesday for the first leg of their tie.
The Associated Press was used in this report.