That they would eventually recover and be back on course to retain their crown was not unexpected – but the man who eventually ended Dortmund’s challenge was as unprecedented as a HBO plot twist.
Claudio Pizarro left the champions all of four years ago, but they had the 40-year-old to thank last weekend as he dealt a blow to their title rivals as devastating as dragonglass to a White Walker – all just months after knocking them out of the DFB Pokal, too.
His 75th-minute equaliser for Werder Bremen means Dortmund are now four points adrift with just two games to play – but a 29th Bundesliga title for Bayern isn’t the only record that can come from it.
At 40 years and 213 days, Pizarro extended his ongoing record of being the league’s oldest ever goal-scorer and, a feat he had achieved with his previous strike against Hertha BSC in February.
"I couldn’t imagine a more worthy successor than Claudio," said previous record-holder, and Bremen midfielder, Mirko Votava. "He’s a great guy and a sporting phenomenon. I’m delighted for him, and he knows that, too."
He already holds the record for the oldest hat-trick scorer, breaking a 31-year-old record with his trio against Bayer Leverkusen back in 2016, and, if he features in Bremen’s final game against RB Leipzig, he will become the oldest player to make a Bundesliga appearance.
It’s not a bad way for Pizarro to bounce back after Robert Lewandowski overtook him as the division’s highest-scoring foreign player earlier this term.
And if his new records aren’t consolation enough, the words of the current Bayern Munich man are sure to be.
"[Pizarro] was strong, he was always calm, his technique was incredible too," Lewandowski said after surpassing his tally.
"He always knew exactly what he wanted to do with the ball and that's what I learned from him. He knew what I had to do with the ball, I have no problem saying that a lot of what I know, I learned by looking at him.”
The Poland international isn’t his only admirer, with former teammate and Anthony Ujah explaining: "To be able to see his movement, how he scores goals and how he moves is an inspiration for me and hopefully I have more to learn from him."
It goes beyond strikers, though, Thiago Alcantara believes.
“Every youngster, not just from South America, can take him as a role model."
He is more than that in the city of Bremen, where he will forever be a Werder legend and their very own King in the North.
When they signed him for the fourth time in the summer – fifth time if you include his 2008-09 loan from Chelsea – coach Florian Kohfeldt stressed that it was a signing about more than football.
“He will have a good influence in the dressing room with his positive energy, conviction and hunger for success,” Kohfeldt said of Pizarro, a man with all the charm and warmth of any hero.
“If he’s fit and healthy, I’m sure he can help us in crucial moments this season. Claudio is a legend and he will get his moments this season.”
He has certainly had his moments, and to have scored six goals – and registered two assists - despite just four starts this term is some feat for the veteran.
But Pizarro has benefited Kohfeldt in another ways too, as the coach explained after Bremen’s 4-0 win over Augsburg earlier this season.
"I let him speak to the lads ahead of Sunday’s game," he said. "His words and his presence are really helpful. He's also valuable to us on the pitch, as seen in the Dortmund game."
The striker’s contributions in all areas helped Werder reach the DFB Pokal semi-finals and now he has his eyes set on taking his Werder army across the continent.
If they get there, will he be leading them on their great adventure?
"We’ll sit down with the club to see what happens in the coming weeks," he said. "I’ve still got the desire and passion to keep playing."
Pizarro has also got the support of the club around him, something which has clearly helped him thrive at Werder and also at Bayern.
“I haven’t been at many clubs, just the ones where I’ve really felt at home,” he explained. “That has been the case at Werder and Bayern and I like to keep in contact with the people at the clubs and in the city. That’s something that’s important to me.”
He’s captured the hearts of both teams, to the point that they are fighting over his post-retirement services, Mein Werder have reported – and with his contributions keeping both Bayern’s title chances and Bremen’s European dream alive, it comes as no surprise.
But, while staying in the north may be, hanging up his boots is not on Pizarro’s mind.
“As long as my body holds up I’ll keep going,” he said – and it certainly is at the moment.