A year after being dumped by Germany head coach Joachim Loew, Thomas Mueller is set to showcase why he is so important for Bayern Munich－and Robert Lewandowski－at Chelsea in the Champions League.

Alongside Borussia Dortmund's Erling Braut Haaland, Bayern's star striker Lewandowski is joint topscorer in the Champions League with 10 goals going into the last-16, first-leg clash on Tuesday.

In order to keep him fresh, Mueller was a second-half replacement in Friday's 3-2 league win over bottom side Paderborn when Lewandowski netted twice.

The Poland striker is on a career-high 38 goals after 32 games in all competitions and is happiest with Mueller alongside him.

"It's easier with Thomas next to me, he helps me out a lot," Lewandowski said of Mueller.

"We always have one player more in the penalty area when he plays, I have more space and not always two or three opponents against me."

It's no coincidence that Lewandowski is enjoying his highest goal tally just when Mueller's 14 assists in Germany's top flight also puts him near his personal best.

Flick switch

The 30-year-old is back to his best after significant setbacks for club and country in 2019.

Alongside fellow 2014 World Cup winners Mats Hummels and Jerome Boateng, Mueller was told last March he was no longer needed by Germany as Joachim Loew rebuilt his squad following the 2018 World Cup debacle.

Then last autumn, Mueller found himself repeatedly benched by Bayern to make room for Philippe Coutinho, who is on loan from Barcelona.

When Niko Kovac was fired in November, caretaker coach Hansi Flick restored Mueller to the starting lineup, often at Coutinho's expense, and he has flourished.

Mueller was superb in the recent 4-1 win at Cologne, drawing defenders to create goals for Kingsley Coman and Lewandowski as Bayern raced into a 3-0 lead after 12 minutes.

With Bayern drawing 1-1 at home to minnow Paderborn on Saturday, Muller came off the bench in the 63rd minute to help steer the host to a 3-2 win. Bayern now leads the Bundesliga standings by a point ahead of RB Leipzig, which triumphed 5-0 at Schalke on Sunday.

Flick is probably wise to pick Mueller, who joined Bayern as a schoolboy in 2000 and made his first-team debut in 2009 just before his 19th birthday.

Such service means he has the ear of the club's senior bosses and an unhappy Mueller is never good for a Bayern coach in the long run.

His relationship with Pep Guardiola became strained after Mueller was benched for the first leg of the 2016 Champions League semifinal defeat at Atletico Madrid.

Mueller was part of a disgruntled group of senior players whose complaints contributed to the firing of Guardiola's successor, Carlo Ancelotti, in 2017 after poor results.

Mueller then became so frustrated under Kovac that his wife Lisa criticized the coach in a social-media post just before he was replaced by Flick.

Space invader

What makes Mueller intriguing is that he identifies neither as a striker nor an attacking midfielder, but rather describes himself as a 'raumdeuter'－an interpreter of space.

He is at his deadliest with perfectly timed runs and quick passes so that his presence in the penalty area creates space for Lewandowski.

"I like to be active in behind the opposition midfield," Mueller has said on his favorite position.

"That's where I can hurt opponents most. I'm a mix between a striker and a midfielder－I'm a raumdeuter."

His success speaks for itself.

A key member of the 2013 team which won the treble of Bundesliga, German Cup and Champions League titles, Mueller has won the domestic league eight times, lifting the German Cup in Berlin on five occasions.

He has scored 38 goals－10 of those at World Cup finals with five each at South Africa 2010 and Brazil 2014－in 100 appearances for Germany.

His current form means he could yet play for his country at a major tournament this summer having been named in the preliminary German squad for the Tokyo Olympics.