Lewandowski was lucky not to be ruled offside when he gave Bayern the lead after just five minutes. Franck Ribery was less fortunate a few minutes later, as his goal was correctly ruled out by VAR. Luck had little to do with it, however, as Bayern completely outclassed Dortmund in the first half, strikes from James Rodriguez and Thomas Muller giving them a 3-0 lead before the half-hour mark.
In the dying minutes of the half, Ribery twinkle-toed his way through the defence to set up Lewandowski’s second, before getting on the scoresheet himself with Bayern’s fifth, lofting the ball elegantly over goalkeeper Roman Burki.
“We were totally absent today,” said Dortmund defender Marcel Schmelzer. “Bayern just played cat and mouse with us. It was a disgrace, and it can’t go on like this.”
After a quiet second half, Lewandowski completed his hat-trick three minutes from time, turning in Joshua Kimmich’s cross from close range.
“I’ve been on the end of a 5-1 defeat here before, so I know how much it hurts,” said Bayern and former Dortmund defender Mats Hummels.
Bayern’s title celebrations remain on hold after Schalke eased to a 2-0 victory over Freiburg earlier in the day.
Daniel Caligiuri put Schalke ahead from the penalty spot on 63 minutes, before Freiburg striker Nils Petersen saw a second yellow card for dissent. With both their striker and their coach Christian Streich sent off, Freiburg capitulated, and Guido Burgstaller secured victory 17 minutes from time.
RB Leipzig survived a late scare in Hanover, battling to a 3-2 victory to break back into the top four.
Leipzig drew first blood on 16 minutes, as Timo Werner broke down the right flank to provide Emil Forsberg with the easiest of tap-ins.
Willi Orban doubled the lead early in the second half, sending a powerful header past Philipp Tschauner. Salif Sane quickly pulled one back for Hanover, before Yussuf Poulsen appeared to secure victory for Leipzig in the 76th minute.
Niclas Fuellkrug fired Hanover back into the game with a flying header, and appeared to complete a dramatic comeback when he found the net again minutes later, only to see his equaliser disallowed for offside through VAR.
“The three points are hugely important for us and we are happy that we got the reward for our hard work,” said Leipzig coach Ralph Hasenhuettl. “But we need to regain stability at the back.”
– Hoffenheim hit six –
Leipzig leapfrog Bayer Leverkusen into fourth, as the latter were held to a turgid 0-0 draw by Augsburg.
At the other end of the table, Hamburg dropped more points as they drew 1-1 in Stuttgart. Lewis Holtby scored his first league goal since August to fire Hamburg into the lead on 18 minutes, but Daniel Ginczek equalised against the run of play for Stuttgart just before half-time.
Hamburg remain bottom, a point behind fellow strugglers Cologne, who were subjected to a 6-0 thrashing at Hoffenheim.
Serge Gnabry scored two brilliant goals to kick-start the rout. Having danced around several defenders to fire in a net-busting opener in the first half, Gnabry grabbed a second just after half-time, picking out the bottom corner from the edge of the box.
Cologne-born forward Mark Uth grabbed a brace, as he and Lukas Rupp scored three goals in the space of 10 minutes. Uth then set up Steven Zuber to prod home Hoffenheim’s sixth.
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