Borussia Dortmund host Tottenham Hotspur on Tuesday needing a win to keep alive their slim Champions League hopes after a terrible run of form.
Spurs visit Dortmund's Signal Iduna Park already sure of a place in the last 16, but victory will see Mauricio Pochettino's side finish top of Group H.
Dortmund, who are third on two points, must beat Spurs and hope Real Madrid do not win at APOEL to maintain a chance of reaching the knock-out stage.
Peter Bosz's Dortmund held a five-point lead in the Bundesliga at the end of September, but since then they have taken just one from a possible 15 points and are fifth following Friday's 2-1 defeat at Stuttgart.
Here are five reasons why it has gone wrong for Dortmund:
Bosz styleBosz took over after Thomas Tuchel was sacked days after winning the German Cup in May for failing to see eye-to-eye with CEO Hans-Joachim Watzke.
Bosz, who led Ajax to last season's Europa League final defeat by Manchester United, prefers a 4-3-3 formation with striker Pierre-Emerick Aubameyang playing off wingers Christian Pulisic and Maximilian Philipp.
However, poor defending leaves huge holes which centre-backs Sokratis Papastathopoulos and Marc Bartra struggle to fill, while Bosz has stood by goalkeeper Roman Burki despite a string of howlers.
"I prefer to work on the Plan A option," Bosz insisted when asked why he does not change tactics during defeats.
Aubameyang's droughtThe Gabon hot-shot is goalless in his last five games. He was suspended for Friday's loss and last scored on October 14.
Aubameyang claims to be baffled by his latest suspension and Dortmund are tight-lipped.
Magazine Kicker said he was late for training and failed to get permission for a video shoot last Wednesday at Dortmund's training ground.
"Aubameyang is actually an awesome lad, but he has no special rights," insisted Watzke.
Bad behaviour is becoming a habit of Aubameyang.
He was suspended for flying to a party in Milan without permission last season and upset the club by shaving the Nike logo into his hair, even though Dortmund are sponsored by Puma.
He then wore a mask for a goal celebration he had donned in a Nike advert.
Burki's blundersThe Dortmund keeper is inconsistent, yet Bosz perseveres with Burki even with veteran Roman Weidenfeller on the bench.
In the last seven games, Burki has leaked 16 goals.
He was at fault at Stuttgart after a horrendous mix-up with defender Marc Bartra led to Chadrac Akolo scoring Stuttgart's opening goal, and could have done better when Josip Brekalo fired through his legs for the second.
Burki's fumble at APOEL last month led to Dortmund drawing 1-1 in the Champions League.
Kevin Trapp is touted as a possible replacement for Burki in the January winter break as the Paris Saint-Germain goalkeeper has lost his starting spot in France.
Dodgy defenceBurki's plight is not helped by playing behind a porous defence, which will invite Spurs striker Harry Kane to attack in midweek.
Bosz made changes after Dortmund were routed 4-2 at Hanover 96 last month after being constantly hit on the break, but Sokratis and Bartra are still unconvincing.
Sokratis' lack of pace is an issue and Bartra's error against Stuttgart was not his first in recent weeks.
"The individual mistakes have been pulling us up this season," said director of sport Michael Zorc.
"The first goal in Stuttgart was almost slapstick."
Mounting pressureWith every defeat, Bosz's situation grows more precarious.
"We can't talk the negative trend away, we need to ask ourselves why we can't produce the same performance from the first few games," said Zorc.
Dortmund have been here before.
They were second from bottom in December of the 2014/15 season, eventually finishing seventh, when then-coach Jurgen Klopp quit before joining Liverpool.
Unlike Bosz, Klopp had credit with Watzke and Zorc after winning two league titles.
German daily Bild claim Dortmund have planned crisis talks for mid-December, meaning Bosz has four weeks to turn it around.