Bayern Munich’s Robert Lewandowski and Thomas Mueller are closing in on the Bundesliga’s record goal-haul for a partnership with the Bavarians reportedly set to spend big to keep the duo together.

Mueller netted twice and Lewandowski scored their third in Saturday’s 3-1 comeback win at home to Darmstadt for the runaway league leaders.

It was Bayern’s last game before Tuesday’s crunch Champions League last 16, first-leg clash at last season’s finalists Juventus.

Lewandowski is the German league’s top scorer with 22 goals, from 21 games, with Mueller on 17.

It leaves the pair with 39 Bundesliga goals between them and 56 in all competitions this season.

They are chasing Grafite and Edin Dzeko’s league record of 54 league goals in the 2008/09 season when Wolfsburg won the title.

SEE MORE: Schedule of Champions League games on US TV and live streaming.

Of course, both Bayern stars already have lucrative long-term contracts.

Lewandowski’s deal until 2019 currently pays him around nine million euros ($10 million) per season, while last December Mueller signed a bumper extension until 2021 — worth a reported 15 million euros per year.

But Bayern want to offer Lewandowski a two-year extension — and would need to raise his pay to around the 18 million euros Real Madrid reportedly wanted to pay him.

With the likes of Manchester City and Paris Saint-Germain also said to be chasing him, Bayern need to ensure their star is happy — and at least as well paid as his team-mate.

German magazine Sport Bild say the first round of contract talks took place in early February when Lewandowski’s advisors Maik Barthel and Cezary Kucharski met club chairman Karl-Heinz Rummenigge and financial director Christian Dreesen.

Kucharski had stirred things up by saying there was “something in” rumors that Real were trying to sign Lewandowski.

However, the Spanish giants now appear to have given up the chase.

Marca journalist Carlos Carpio tweeted on Friday that chasing Lewandowski’s signature is no longer “considered a priority” by Real, because “he is close to renewing with Bayern”.

– Future preparations –

Lewandowski took heart when fellow Bayern stars Jerome Boateng, Xabi Alonso and Mueller all signed contract extensions before Christmas.

“Of course, I have recently noticed how the club is preparing for the future,” the 27-year-old told Sport Bild.

“For players like Jerome Boateng and Thomas Mueller to extend is a sign Bayern can keep their players despite the money in England.

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“I know there are prospects abroad, but I can imagine staying here… because the club is known to recognize achievements.”

In short: they pay well.

Poland’s Lewandowski forged a reputation as one of the world’s top strikers in four seasons at Borussia Dortmund.

Despite Dortmund’s best efforts to keep him, he walked away to join rivals Bayern on a free transfer in 2014.

Bavarian born-and-bred with a thick accent, Mueller is the team joker for both club and country and rose through Bayern’s academy.

He has held down a first-team place since the start of the 2009/10 season.

Bayern has already turned down a reported bid for him of over 100 million euros from Manchester United.

“Yes, there were offers,” Mueller told Saturday’s edition of Munich newspaper AZ.

“But we are in the top three (clubs) in Europe with Barcelona and Real Madrid.

“The English are very powerfully financed, but whether they return to the top of European football remains to be seen.

“From a sporting perspective, it was easy to extend here.

“When the (Bayern) contract expires, I’ll be over 30, but I think I can keep the level over the next few years in order to be successful here.”

Lewandowski has offered no such commitment, especially with Carlo Ancelotti to replace Pep Guardiola as Bayern’s head coach next season.

“Many times I have heard players say such a thing and then comes another coach and they were no longer in such high demand. Or they got a very interesting offer,” he told Die Welt.

“In any case, I feel very well at Bayern and will always give everything for the team while I’m here.”