The 20-year-old Bayern Munich midfielder scored twice in Germany's 4-1 hammering of England last Sunday and is a contender for the tournament's best young player. But he was virtually unknown outside of Germany when he made his debut in a 1-0 friendly defeat to Argentina in Munich in March and attended the post-match press conference as his country's great new hope alongside the Argentina coach.
Maradona joked he thought the ballboy had arrived and felt so slighted that he stormed off and refused to return until the German left the stage to him alone. But with three goals at this World Cup already and a Champions League final appearance, plus the German league and cup double, under his belt, Mueller is now a household name and sure to cause Argentina problems in Cape Town on Saturday.
"Now I have won two titles and played in the Champions League with Bayern, so a few things have changed," said Mueller. He is too young to remember Maradona as a player, but he saw the midfield maestro play in former Germany captain Lothar Matthaeus' testimonial game in 2000 and was greatly impressed.
"He was overweight at that time but what he did with the ball was amazing, something I have rarely seen," he said. "As a coach I can't judge him but the results and the convincing way Argentina are playing means he is doing things right."
When Germamy last played Argentina in the World Cup quarter-finals at Berlin's Olympic Stadium four years ago, Mueller watched the game with friends on a giant screen in Munich and well remembers the 4-2 penalty shoot-out win.
"I remember us winning through sheer willpower and I haven't forgotten the scenes after," he said, referring to the skirmishes between players from both teams on the pitch after Germany's Jens Lehmann saved the final penalty. "We musn't be provoked," warned Mueller ahead of this weekend's clash in Cape Town, before joking: "I won't mind a fight afterwards if we have won."