"We were exhausted at the end," Bayern centre-back Mats Hummels told Sky Sport. "Mainz passed the ball well but we deserved to win."
Bayern profited from Bayer Leverkusen’s 0-0 draw at Freiburg to increase their advantage. However the lead will be cut to 17 points if Eintracht Frankfurt win at Augsburg on Sunday.
On Friday night, Michy Batshuayi made a dream debut for Borussia Dortmund at Cologne. The 24-year-old Belgium international scored twice in the 3-2 Bundesliga win that took Dortmund temporarily up to second. They dropped to fourth place on Saturday following Leverkusen’s draw and Leipzig’s 1-0 win at Borussia Moenchengladbach.
Just before the January transfer window closed, Dortmund sold the Gabon international Pierre-Emerick Aubameyang to Arsenal for 63 million euros and then signed Batshuayi on loan from Chelsea.
"I am very happy, but the most important thing was the win," Batshuayi told Eurosport. "It's my first match, it was always going to be difficult. I could have scored more but the most important is the win and the three points.”