Bottom side Hamburg have just five games left to avoid a historic relegation from the Bundesliga after Sunday's 1-0 defeat at Werder Bremen in the north German derby.
Bremen's Argentine striker Franco di Santo claimed his 13th goal of the season by netting an 84th-minute penalty just after Hamburg's Swiss midfielder Valon Behrami was sent off -- on his 30th birthday -- for pulling down Werder's Zlatko Junuzovic in the area.
Hamburg have now lost their last five games, taking just two points in nine matches, as Bruno Labbadia suffered defeat in his first game since being appointed as Hamburg's fourth coach this season on Wednesday.
"To lose a game with a penalty like that is bitterly disappointing," said Labbadia, who is in his second stint as Hamburg boss.
"For me that was never, ever a red card."
The only side to have never been relegated from Germany's top flight, Hamburg are four points from safety having only avoided the drop last season by winning a play-off.
Meanwhile leaders Bayern Munich are on the verge of a third Bundesliga title after Saturday's hard-fought 2-0 win at Hoffenheim, but have fresh injury worries for Tuesday's crucial clash against Porto.
Bayern face a make-or-break Champions League quarter-final second leg against Porto in Munich having lost 3-1 in Portugal in the first leg, but have eight players injured.
Left-back Juan Bernat had to be helped off after a bone-crunching first-half tackle in Hoffenheim, but coach Pep Guardiola said the Spaniard was only taken off as a precaution.
"We didn't want to take any risks," he added.
With second-placed Wolfsburg at home to Schalke on Sunday, Bayern extended their lead to 13 points with five games left.
Depending on results elsewhere, next Saturday's clash at home to Hertha Berlin could see Bayern confirmed champions after Sebastian Rode's first-half strike and an own-goal from Hoffenheim captain Andreas Beck gave them three more points.
Meanwhile, Borussia Dortmund enjoyed a 3-0 victory at home to relegation-threatened Paderborn to climb to eighth in their first game since coach Jurgen Klopp announced he would be leaving at the end of the season.
Having won the 2011 and 2012 titles, then finished runners-up to Bayern for the last two years, Klopp will quit Dortmund next month after seven years in charge while ex-Mainz boss Thomas Tuchel was confirmed as his replacement on Sunday.
Second-half goals by Henrikh Mkhitaryan, Pierre-Emerick Aubameyang and Shinji Kagawa left Dortmund in ninth and just outside the Europa League places.
After Borussia Moenchengladbach's goalless draw at Eintracht Frankfurt on Friday, Bayer Leverkusen took Gladbach's place in third, and amongst the automatic Champions League berths, with a 4-0 mauling of Hanover 96.
It was Leverkusen's seventh straight league win, a new club record.
Centre-backs Omer Toprak and Kyriakos Papadopoulos as well as forwards Julian Brandt and Stefan Kiessling scored to put Leverkusen level with Gladbach on 54 points, but ahead on goal difference.
Ausgburg went up to fifth and remain on course for a Europa League spot with a 2-1 home win over second-from-bottom VfB Stuttgart, thanks to goals by Tobias Werner and Paraguay striker Raul Bobadilla.
Mainz are 11th after Japan striker Shinji Okazaki scored twice in their 3-2 win at relegation contenders Freiburg on Saturday.
Mid-table Hertha Berlin and Cologne both stay seven points above the relegation places following their goalless draw in the capital.