BERLIN (AP) — Union Berlin’s punishing schedule finally took its toll Sunday as it conceded five second-half goals in a 5-0 defeat at Bayer Leverkusen that left Bayern Munich top of the Bundesliga after 13 rounds.

Moussa Diaby scored twice and Adam Hložek and Mitchel Bakker added two more after Robert Andrich broke the deadlock against his former club right after the break.

“Bayer pulled the plug on us with that. In the end, you have to be maybe more secure and not run into an open knife. We can do it better,” Union coach Urs Fischer said of his team’s disastrous second half. “We were often not consistent in defense. That can be done differently, too.”

It was Union’s heaviest defeat of the season after it previously had the meanest defense in the league with only nine goals conceded in 12 games.

Union’s third defeat left Bayern one point clear of Freiburg with two rounds remaining before the league’s extended winter break to accommodate the World Cup in Qatar.

Freiburg moved second with a 2-0 win at home over Cologne in Sunday’s late game. Second-half goals from Jeong Woo-yeong and Michael Gregoritsch ensured Freiburg became Bayern’s closest challenger with Union dropping to third, two points behind 10-time defending champion Bayern.

Some Freiburg fans displayed a banner saying “Boycott Qatar 2022” during the game, continuing widespread protests across the Bundesliga against the upcoming World Cup over human rights abuses in Qatar.

Union, which was only promoted for the first time in 2019, had been top for seven weeks since a 1-0 win at Cologne on Sept. 11.

Union had won eight of its last nine games and had traveled to Leverkusen directly from its 1-0 Europa League win over Royale Union Saint-Gilloise in Belgium on Thursday.

Union coach Urs Fischer made four changes to his lineup from that game but was unable to compensate for Leverkusen’s fresher legs as the home team ran riot in the second half.

Leverkusen coach Xabi Alonso also made four changes to the team that drew 0-0 with Club Brugge in the Champions League on Tuesday.

Both teams canceled each other out in a lackluster first half with few highlights.

Then Andrich broke the deadlock right after the break with a low shot after a corner. He didn’t celebrate out of respect for his former team, but his teammates had no such restrictions.

The next goal was a gift from goalkeeper Lennart Grill — who is on loan from Leverkusen — when he failed to control a back pass and the ball fell to Diaby, who raced clear of the despairing Union defenders to score off the left post.

The French forward grabbed his second two minutes later, finishing off a counterattack started by Mitchel Bakker as Union had pushed for a response.

Fischer reacted with three changes at once, but Leverkusen maintained its dominance. Grill denied Diaby a hat trick.

Nadim Amiri crossed for Hložek to score his first Bundesliga goal with his heel in the 68th, then Hložek set up Bakker for the fifth in the 76th.

“The second half was extremely unfavorable,” Union midfielder Rani Khedira said. “We started badly and before you know it, it’s 5-0. This is unfortunately a total failure that has happened to us now and it will not happen a second time.”

The win lifted Leverkusen out of the relegation zone. It was only its third league win of the season.

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