Roger Federer returned to action after three months out with a loss to 39-year-old Tommy Haas, but insisted he was not surprised by the defeat.
It was only the second defeat of the year for Federer, who missed the entire clay court season, opting instead to rest and focus on the upcoming grass court season as he looks to steal a march towards a possible eighth Wimbledon title.
Haas, a former world number two, is currently ranked way down in 302nd place, but, having gone a set down, was able to haul himself back into it, overcoming a match point before eventually coming out on top in a fantastic match in Stuttgart.
For some, the result came as a bit of a shock, especially considering the kind of form Federer has shown in the earlier stages of 2017.
However, the veteran Swiss was not in the least surprised by Haas' performance.
"I'm not so shocked to have lost. I knew I could lose against Tommy," said Federer.
"He was so good at the end and if I am happy for anybody, then it's for Tommy."
The match was the oldest match on the tour since 1982, with the combined age of the two coming in at 74.
Haas, who is in his farewell season, has not made a quarter-final since 2014 and was understandably pleased with his performance.
"It's always special to play a close friend like Roger on grass, always lots of emotion," said Haas, who has undergone nine surgeries in his career to mend a number of ailments.
"I saved a match point in the second set so was able to play more freely after that. I even shocked myself."
Haas's victory over Federer broke a few long standing records.
The German became the oldest player to beat a top-five opponent since Jimmy Connors defeated Michael Stitch in 1992.
He also became the lowest-ranked player to beat Roger Federer since 1999, when 407th ranked Bjorn Phau beat the Swiss maestro in Washington.
Having survived a match point in the second set tie-break, Haas took control of the decider cruising to victory in the end by a score of 2-6, 7-6 (10-8), 6-4.
He will face fellow German Mischa Zverev in the next round.
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