One of the many men who travel the world, playing in the less noticed tournaments, picking up the more modest appearance fees, Mullers record and age suggested he would end his career as barely a footnote in the annals of the sport.
His second round appearance at the All England Club last year was barely noticed, understandably for a player who had made the last eight at a Grand Slam event just once in his career — at the US Open in 2008.
On Monday though, the left-hander produced one of the most memorable upsets in the history of Wimbledon — beating 15-times Grand Slam winner Rafael Nadal in an astonishing 6-3, 6-4, 3-6, 4-6, 15-13 battle that lasted four hours and 48 minutes.
Muller puts his delayed emergence down to a 2013 elbow injury that, almost threatened his career, kept him off the courts and let him work on fitness.
“This is definitely the biggest victory since then, since I came back, especially at that stage of a Grand Slam, playing one of the guys who is dominating the tennis this year again. Definitely the biggest win,” he said.
“Since 2014 when I came back, Im able to play full seasons without any breaks during the season. I have a lot of confidence in my body now, which I didnt have before.
“All this is changing a lot for me. For sure that has been the key for me in the last few years, to be that successful.” He can be an awkward opponent with his fondness for old-school serve-and-volley play.
Although he had beaten Nadal 12 years ago at Wimbledon, few gave him a chance on Monday against the fourth seed and French Open champion.
But Muller has risen up the rankings this year, capturing his first two titles on the tour, in Sydney earlier this year and then on grass at Den Bosch in the lead up to Wimbledon. He is ranked 26th in the world but his comfort on grass earned him a 16th seed at Wimbledon.
Cool to the point of being emotionless, Muller coped with giving up a two-set lead to the Spaniard and then continued, unruffled, through the marathon two hours 15 minutes final set before finally sealing victory.
Nadal disappointed
Nadal struggled to hide his disappointment after his attempt to reclaim the Wimbledon crown he last won seven years ago fell apart.
The 31-year-old Spaniard had rolled back the years in reaching the fourth round and seemed in the mood, and form, for a serious title assault just weeks after winning the French Open for a 10th time.
Magnanimous as ever, 15-time Grand Slam champion Nadal made no excuses, admitting Muller was the better player, but said he had wasted a golden opportunity to go all the way.
“I had my chances, and he had some mistakes, but not enough,” Nadal, who returned to form at the start of the year when reaching the Australian Open final, told reporters. “It’s true most of the time in the fifth set he played more aggressive and he played better than me.
“I played well for moments, but I was a lot of times fighting against the score, too many times in the fifth,” added the former world number one.
“Finally, the normal thing when you are in the situation too many times, is finally you lose. Thats what happened.
“Its not the result that I was expecting. I played better than other years, true. At the same time I was ready for important things, so I lost an opportunity.”
Until Monday, Nadal had not lost a set in Grand Slam play since losing Januarys Melbourne Park final to Roger Federer. However, this was not to be his day.
