Bayer Leverkusen were let down by defensive failings as they opened their campaign with a 2-0 defeat to Mainz.
Visitors undone by goals from Allagui and Toprak
Bayer Leverkusen were let down by defensive failings as they opened their Bundesliga campaign with a 2-0 defeat to Mainz on Sunday.
Goalkeeper Fabian Giefer's poor clearance allowed Sami Allagui to open the scoring before half-time and Omer Toprak's late own goal ensured there would be no way back.
Thomas Tuchel's side suffered a shock Europa League elimination on penalties against Romanian minnows Gaz Metan in the third qualifying round, and will have been keen to respond in front of their home fans at the new Coface Arena.
They were almost behind inside eight minutes, though, when Stefan Reinartz met Daniel Schwaab's free-kick with a powerful header which was blocked by keeper Heinz Muller.
But Reinartz's back-pass led indirectly to the home side's opener in the 32nd minute. Geifer, selected in place of David Yelldell following Bayer's 4-3 defeat to Dynamo Dresden in the German Cup, sliced his clearance and Allagui controlled the ball and finished from an acute angle.
The visitors struggled to find a response as the second half became bogged down in a midfield battle, and it was Mainz who threatened next. Allagui tried his luck from 25 yards but Giefer partially redeemed himself for his earlier howler by strongly parrying the shot away.
Switzerland forward Eren Derdiyok went closest to an equaliser in the 77th minute, but his 12-yard drive was parried by Muller.
And the hosts made sure of victory with four minutes left on the clock as Toprak slid in to prevent Marco Caligiuri's cross reaching Andreas Ivanschitz but could only divert the ball into the bottom corner of his own net.
