Nothing was signed, sealed or delivered on Matchday 28, though the picture is becoming that little bit clearer as the title race edges closer to a premature conclusion, with plenty still to play for at the top and bottom.

bundesliga.com runs down the five main takeaways from the latest round of Bundesliga action...

1) Bayer on the brink of glory

No, it is not a typo. Bayer, without the final 'n', are on the brink of lifting the Bundesliga title. Bayer Leverkusen extended their unbeaten record this season to 28 matches, equalling the Bundesliga record shared by Pep Guardiola's Bayern Munich and Jürgen Klopp's Borussia Dortmund in 2013/14 and 2011/12 respectively. Those runs ended on Matchday 29, but the title was ultimately wrapped up, and Leverkusen can do the same next weekend – even before they welcome Werder Bremen to the BayArena on Sunday.

Thanks to a Florian Wirtz penalty, Die Werkself saw off Union Berlin in the capital – where they will return again in May for the DFB Cup final – and open up a 16-point lead over Bayern and Stuttgart, with just 18 points left to play for this season. No club has ever let such an advantage slip at this stage of a season, and there is nothing to indicate that the Neverkusen days will continue as Xabi Alonso's men prepare a title party in front of their own fans.

The Meisterschale will be theirs with a win over Werder, but the champagne corks could pop already on Saturday night, should both Bayern and VfB Stuttgart fail to win their fixtures with Cologne and Eintracht Frankfurt respectively. Either way, it looks like the booze can be readied.

Watch: Highlights of Leverkusen's 1-0 win at Union Berlin

2) Stuttgart the new 'Stern des Südens'?

The club anthem which booms out at Munich's Allianz Arena every other week hails the 'Stern des Südens', Germany's Southern Star. With a record 32 Bundesliga titles to their name, Bayern have earned their reputation not only as the star club in southern Germany, but also of the entire nation, though their status on both accounts is under threat. Stuttgart, from the neighbouring southern German state of Baden-Württemberg, have almost stealthily sneaked up on their illustrious rivals, and drawn level.

Bayern's dwindling title challenge all but evaporated when they squandered a two-goal lead at Heidenheim to go down 3-2, and Stuttgart took full advantage with a Serhou Guirassy fires VfB Stuttgart a step closer to UEFA Champions League in Dortmund win | Bundesliga which took them closer to securing UEFA Champions League football next season. Serhou Guirassy was Stuttgart's hero with his 24th goal of the season – a joint club record with Mario Gomez (2008/09), and combined with the 15 goals scored by Deniz Undav, they are the most prolific strike partnership in the club's history.

Watch: Highlights of Stuttgart's 1-0 win in Dortmund

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With eight wins in their past 10 games, Stuttgart have not only crept up on Bayern, they have moved to within one single point of securing their place in Europe next season, less than 10 months after coming through a play-off to avoid relegation to Bundesliga 2. Sebastian Hoeneß' men also put seven points between themselves and Dortmund, who dropped to fifth, meaning that a place at European football's top table will be theirs with a handful more victories.

3) Candles blown out for birthday boys Dortmund

It should have been a day of celebration, but when the candles were blown out on the 50th birthday of Borussia Dortmund's iconic Signal Iduna Park home, few were in the mood for celebrations. The 81,365-capacity arena, boasting the famous, enviable Yellow Wall – the largest terrace in Europe – is sold out every week, but it was reduced to a stunned silence on Saturday evening as Stuttgart inflicted what could prove to be a very costly defeat.

With RB Leipzig winning 4-1 at Freiburg, the two clubs exchanged places in the Bundesliga standings on Matchday 28, with six games of the season to go. The significance of finishing in the top four will be highlighted to them quite vividly on Wednesday, when they travel to Atlético Madrid for the first leg of their Champions League quarter-final clash. A fifth-placed finish could still be enough depending on how the Bundesliga's remaining European trio fare, but there are no guarantees.

Watch: Schlotterbeck reflects on 'painful' defeat

A critical few weeks therefore lie in store for Edin Terzić's men, who have barely had the time to revel in their Klassiker win over Bayern. A win in Madrid would be just the tonic ahead of the next three league fixtures, which feature a battle of the Borussias, the visit of champions-elect Leverkusen and the potentially decisive trip to Leipzig on Matchday 31.

4) Heidenheim are here to stay

When the fixture list was announced back in July, fans of Heidenheim will have been putting a big, fat circle around Matchday 28 – the day when Bayern would come to town. Few Heidenheim fans would have gone as far as to predict a win for their side against the record champions, and perhaps only the most optimistic would have expected them to be in a position of mid-table safety and able to enjoy such a game. Yet if it was not yet clear to everybody before, it most certainly is now: Frank Schmidt's men have proven Bundesliga pedigree.

In their first ever season in Germany's top flight, Heidenheim have brought a real breath of fresh air to Germany's top tier, going about their business without a care in the world and defying the critics who predicted an immediate return to Bundesliga 2. Indeed, Schmidt has changed very little of the formula which has catapulted his team from the fourth division to the Bundesliga in his 16 years at the helm: be bold, be brazen and believe. Saturday's comeback victory typified everything this club is all about: trailing 2-0 at half-time, two goals from Tim Kleindienst and a Kevin Sessa strike completed a second-half turnaround which all but mathematically secured a second season in the Bundesliga for a club who can also now boast Bayern as a major scalp.

Watch: Tim Klendienst on 'historic' Heidenheim win

5) Rollercoaster relegation ride

If Matchday 28 is anything to go by, it is going to be quite a ride between now and the end of the season for up to eight clubs still in the relegation mix. The drama of a relegation dogfight could be encapsulated into just two minutes of Cologne's come-from-behind win over Bochum, which gave the Domstädter some much-needed belief, when they were looking dead and buried. That 2-1 success was an essential response to Mainz's 4-0 win over Darmstadt, which practically condemns Torsten Lieberknecht's men to an immediate return to Bundesliga 2.

Watch: Cologne recorded a dramatic win over Bochum

Cologne remain a point adrift of Mainz, who occupy the relegation play-off berth, but crucially the gap to Bochum has been cut to four points. Just ahead of Bochum, new Wolfsburg coach Ralph Hasenhüttl has seen the size of his task after a 3-1 defeat to Borussia Mönchengladbach left his side still just within five points of the bottom three, while Union Berlin's defeat to Leverkusen has them just a single point closer further from the drop zone. Werder will be in no mood for being part of Leverkusen's possible title party next weekend, with just six points separating them from the dreaded 16th-place, and Gladbach are ahead of them only on goal difference.

All eight clubs are still set for a nailbiting end to the season.

About the clubs

Bayer 04 Leverkusen

BayArena

1. FC Köln

RheinEnergieSTADION

FC Bayern München

Allianz Arena

Borussia Dortmund

SIGNAL IDUNA PARK

1. FC Heidenheim 1846

Voith-Arena

1. FSV Mainz 05

MEWA ARENA

RB Leipzig

Red Bull Arena

VfB Stuttgart

MHPArena