A goal after just 33 seconds from Marco Reus was all that separated the sides until the final minutes of what, nonetheless, was an overwhelmingly one-sided affair. Robert Lewandowski put the result beyond doubt in the 87th minute - the Polish frontman in the process extending his remarkable scoring run to twelve consecutive games in the Bundesliga, taking him within four of the legendary Gerd Müller's all-time best mark.
Dortmund roar out the blocks
The result leaves Dortmund still eight points clear of third-place Bayer Leverkusen, and now 15 ahead of Schalke in fourth - who after themselves losing on Saturday are no longer able to deprive their near-neighbours of a top-three finish. For Mainz, now with just one win in their last eleven outings, the dream of a UEFA Europa League slot is meanwhile slowly but surely turning to dust.
Jürgen Klopp started a close to full-strength side against the club where he spent so long as a player before also making his breakthrough there as a coach. With Mats Hummels restored to the centre of defence alongside Neven Subotic, skipper Sebastian Kehl was the only first-teamer missing due to injury. Ilkay Gündogan dropped back into one of the holding slots, with Reus taking up an advanced midfield role, and inside the first minute he had the ball in the net to put the Yellow-Blacks in front. Mario Götze chased down a long ball from Mats Hummels, FSV keeper Christian Wetklo made a hash of his attempted clearance and Reus, following up, was presented with the easiest of finishes.
Chances go begging
Having set the tone at the earliest opportunity, BVB pressed forward in search of a quick second and Wetklo dealt far better with Reus's next effort, a blistering drive in the sixth minute. The Mainz custodian came to his side's rescue again on the quarter-hour mark, saving at point-blank range from Subotic following a corner.
Borussia were looking in the mood, but Marcel Risse finally carved out a half-chance for the visitors midway to the break, setting up Nikita Rukavytsya for what turned out to be a total miscue at the far post. In response, Lewandowski curled a shot just wide at the end of a fine interchange between Reus and Götze. That, for the most part, was that as far as the chances went through to the interval, as Borussia switched down a gear and the visitors struggled to create any kind of forward momentum themselves.
Lewandowski still on course
Within three minutes of the restart, Mainz carved out a better chance than they had in the entire course of the first half, Niki Zimling blasting a thunderbolt none too far over the bar. The action shifted swiftly back to the other end after that, though, with two chances inside as many minutes for Marcel Schmelzer. The full back's first effort slid inches wide of the far post, his second - following an FSV defensive mix-up - did likewise.
Dortmund upped the tempo now, seeking to kill the game off as a contest, and Reus should have done better with a wonderful pass from Nuri Sahin than blast it over the bar from the level of the penalty spot. With just under quarter of an hour to go, Hummels nearly crowned his starting comeback with a goal, Bo Svensson somehow scraping his header off the line from another dangerous BVB corner. It was beginning to look like the hosts would have to settle for a single-goal success, but then, with three minutes of regulation tiome to go, sub Moritz Leitner and Lukasz Piszcek combined to free up Lewandowski for a straightforward finish, and it was definitively game over.
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