Xabi Alonso's Leverkusen can become the first team in Bundesliga history to go through a campaign unbeaten by avoiding defeat against Augsburg.
Not even the greatest Bayern Munich sides have managed an invincible season.
That Alonso's men have done it without losing in any competition - a European record 50-game streak which includes runs to next week's German Cup and Europa League finals - shows how incredible they have been.
A win against Augsburg would net Leverkusen 90 points from 34 games - the equal second-highest tally in German football history.
Leverkusen striker Patrik Schick said the match was "like a final", while captain Lukas Hradecky said his team had "immortality" in sight.
Regardless of the result, Leverkusen will hoist the Bundesliga shield on Saturday and Hradecky said he would "be careful" not to hold it upside down, like Stuttgart captain Fernando Meira did in 2007.
In the German capital, Union - who faced Real Madrid in the Champions League in December - need to beat Freiburg and hope for other results to go their way in order to avoid relegation.
Union won at home on the final day last season to finish fourth and qualify for Champions League football, continuing the team's rise after their debut promotion in 2019.
Remarkably, Union sat atop the Bundesliga standings after two games this season, but then fell to rock bottom after a run of nine straight losses.
In 16th spot, Union need a point to avoid falling through the trap door.
Even then, staying in 16th will still mean a two-legged playoff against Fortuna Duesseldorf, who finished third in the second division.
Duesseldorf boast a 52,000-seat stadium and are in incredible form, having not lost in the league since early February.
For Union, even a win will not guarantee safety. Union will only be safe if one of Mainz, who play at Wolfsburg, or Bochum, who travel to Werder Bremen, lose.
Freiburg coach Christian Streich, who signs off from a 14-year tenure at the club against Union on Saturday, said his side were "going to play to win".
"For Union, it's about staying in the league. They will certainly do everything they can to stay in it, and we will do everything we can to have a nice finish."
Champions League finalists Borussia Dortmund host last-placed Darmstadt in Marco Reus' final game at the Westfalenstadion.
Bayern Munich will guarantee second spot with probably just a draw against Hoffenheim while Harry Kane requires six goals to beat Robert Lewandowski's single-season record of 41.
One to watch: Christopher Trimmel (Union Berlin)
Union Berlin captain Christopher Trimmel extended his deal with the relegation-threatened club by one year until 2025 on Thursday, promising "the story isn't over yet."
Trimmel joined Union in 2014 and is the only player remaining from the club's first-ever promotion, back in 2019.
The Austria defender has tasted the highest of highs with Union, saying "together we have achieved more than I ever imagined. Union fans, I'm staying."
Key stats
0 - No team has ever gone through a Bundesliga season unbeaten. Leverkusen are a game away.
71 - Last season, Bayern won the title on 71 points, beating Dortmund on goal difference. If Stuttgart beat Gladbach, they will join Leverkusen and Bayern in having more than 71 points.
17 - Darmstadt have 17 points with a game to go. Only three teams in Bundesliga history have ever recorded a worse points tally.
