Borussia Dortmund may have done the Bundesliga proud this week. They didn’t do FC Köln any favours on Saturday night. After the Champions League finalists’ meek 3-0 defeat at Mainz, Edin Terzic and Marco Reus were sheepish and apologetic, with the coach bemoaning the display as “the face we’ve shown far too often this season”.

No matter. It takes a lot to dampen the spirits of the people of Cologne at any time, but on this Saturday? Nothing was going to smother the fire in their hearts. Their Effzeh had snatched victory from the jaws of certain defeat in a manner that stunned a stadium and city in which people want to believe anything, everything, is possible. They couldn’t quite believe this. “We were already relegated,” defender Timo Hübers told Sky afterwards. “We were mentally and physically exhausted.”

Hübers does not exaggerate. His team were done, still trailing at home to Union Berlin with a touch over three minutes of normal time to go and knowing that only a win would do. And they had only managed four of those before in a tough season underpinned by injuries, a transfer ban, a beloved coach being forced to take his leave and the lowest goals-for tally of any Bundesliga team. A fairytale, however improbable, normally needs a hero, wit, invention and for a long time, Köln have appeared to have none of those ingredients.

What happened next might slide down the page and become a mere footnote in history if, as we’ve expected for weeks if not months, FC Köln are relegated from the Bundesliga for the seventh time in their history at the same time next week. If it keeps them up? People will be retelling the stories over constantly refilled glasses of Kölsch in bierkellers for decades. And they won’t need to embellish one bit, because the plain truth is extraordinary enough.

Steffen Tigges’s equaliser, nodded in from a Mark Uth mis-hit, already felt like it was the Effzeh attack operating at its maximum. In the dozen games that preceded this one, Köln had only twice scored more than once, in the 3-3 derby draw at Borussia Mönchengladbach and in the similarly miraculous late, late win over Bochum. The other 10 games yielded a meagre five goals. Yet as stoppage time ticked on, seconds after András Schäfer fluffed a very presentable chance to put the visitors back ahead, Linton Maina found the energy to drive to the byline one more time, stood the ball up and Damion Downs – 19 years old, and still to start a Bundesliga game for the club – nodded home in front of the Südkurve to spark pandemonium. Even the normally reserved coach Timo Schultz joined the pile on.

Malleable, vulnerable opponents in Union certainly helped. A team that had plummeted under the increased strains of Champions League participation in the season’s first half appeared to have saved themselves with the power of their Köpenick home by spring, but have slipped back towards the trapdoor in recent weeks. The club took the decision to fire Nenad Bjelica as coach in the week with only two games to go this season. The short, sharp shock seemed to have worked as Union led by two goals within the first 20 minutes. Now, the Berliners face a beyond nervy final day of a season which began with so much hope.

In isolation, this comeback would have been extraordinary but Köln have looked buried for weeks. The last home game with Freiburg, in which they were full of desire but bereft of craft, felt like the end. The rousing reception the Südkurve gave their team after the previous Friday night home game with Leipzig felt more wake than motivation, the evidence clear. The opposition were excellent but they had only had to be so intermittently to win at a canter. This FC Köln were simply not good enough for the top flight.

But here they were, having not discernibly improved in the interim – “in the last few weeks,” said Schultz, “only the other teams have managed to play for us. Now we have managed to play for ourselves.” Their managing director, Christian Keller, looked like a nervous wreck on the sidelines. A bespectacled Jonas Hector, the captain who retired at the end of last season and who they have missed so much, stood clenching teeth and fists up in the stands, Effzeh’s version of Maradona watching as a fan at Boca. And on the other side there was a shell-shocked Marco Grote, left holding the baby as Union’s caretaker coach for the second time this season and looking ashen-faced ahead of their date with destiny next week.

Because this isn’t the last miracle Köln will need. On the final day they will need to win again, at Heidenheim, and hope Union lose at home to Freiburg. Even then, they wouldn’t be safe, with a two-legged playoff against Fortuna Düsseldorf to be negotiated, and one senses the gap between top-tier strugglers and second-tier hopefuls is not as great as it habitually tends to be, often destroying any tension. Yet at this club, in this city, hope springs eternal. As always.

Talking points

• Dortmund’s lethargic return to domestic action was in stark contrast with their vanquishers Mainz, who hit their visitors with three goals in the opening 23 minutes and underlined their startling improvement under Bo Henriksen (they haven’t lost since March’s 8-1 defeat at Bayern), sparking celebrations on the pitch and in the stands. The result made sure the 05ers can’t be directly relegated and, barring a goal-difference miracle, a point at Wolfsburg on the final day would guarantee them not falling into the playoff spot either. BVB’s loss means Leipzig have mathematically clinched fourth, though fan grumblings about Marco Rose’s tactics in the 1-1 draw with Werder Bremen are worth keeping an eye on.

• What better therapy for Bayern after their agonising Champions League exit than a visit from their bunnies, Wolfsburg? They were missing an injured Harry Kane – surely finishing any slim chance he had of eclipsing Robert Lewandowski’s single-season goal record – but eased home 2-0 with teenager Lovro Zvonarek scoring barely three minutes into his first Bundesliga start.

• We now know the two automatically promoted teams to the Bundesliga; Holstein Kiel’s draw with Fortuna Düsseldorf on Saturday sent them into the top flight for the first time, while St Pauli’s comfortable 3-1 win over relegated Osnabrück not only sealed their promotion back to the Bundesliga after a 13-year absence but left them in pole position to win the title on the final day.

• After 12 and a half years in charge of the first team, Christian Streich took control of Freiburg for one last home game, an emotional 1-1 draw with Heidenheim. One banner in the stands read “loyalität und ehrlichkeit, leider eine seltenheit” (loyalty and honesty, unfortunately a rarity). Streich is a one-off who will be missed, and not just by Freiburg fans. He could still sign off by returning the club to European competition for what would be an unprecedented third straight season, the twist being that SCF’s goal difference means they may need to win at Union to make sure.