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 Erling Braut Haaland, Bayern's star striker Lewandowski is joint top-scorer 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 has 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.
Flourishing under Flick
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 sacked in November, caretaker coach Hansi Flick restored Mueller to the starting line-up, often at Coutinho's expensive, and he has flourished.
Mueller was superb in their 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.
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 lengthy 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 2016 Champions League semi-final, first-leg defeat at Atletico Madrid.
Mueller was part of a disgruntled group of senior players whose complaints contributed to the sacking of Guardiola's successor Carlo Ancelotti in 2017 after poor results.
Mueller then became so frustrated under Kovac that his wife Lisa criticised the coach in a social media post just before he was replaced by Flick.
What makes Mueller unique is that he is neither a striker, nor an attacking midfielder, but 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 the space in behind the opposition's midfield," Mueller has said on his favourite position.
"That's where I can hurt the opponent 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 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 Germany at a major international tournament this summer having been named in the preliminary German squad for the Tokyo Olympics.