Munich (Germany) (AFP) - Alexander Zverev was dumped out in the last 16 of the ATP tournament in Munich, suffering a straight sets defeat to Christopher O'Connell on Thursday.
Competing on home soil, Zverev lost 7-6 (7/2), 6-4 to the Australian, who is ranked 82nd in the world.
O'Connell converted his first match point just short of the two-hour mark to make it through to the last eight.
Zverev took the court on his 26th birthday, a day later than planned after rain postponed the last 16 clash from Wednesday.
In cold temperatures, the 16th-ranked Zverev took time to warm up, losing serve early in the first set.
A strong home support cheering on helped the Hamburg native fight back to force a tiebreak, but he made a number of errors close to the net as he fell behind.
Zverev broke back late in the second to level at 4-4, but lost the following two games to lose the set and the match.
Top seed Holger Rune eliminated Yannick Hanfmann of Germany, also in straight sets.
Rune, up to a career-high ranking of seventh after reaching the Monte Carlo final last week, shrugged off the cold weather as he advanced 6-3, 6-4.
"I'm from Denmark," the 19-year-old said. "At the beginning of the season there are always days like this and sometimes it's even worse."
World number 10 and second seed Taylor Fritz continued his strong start to the European clay-court season with a debut win in Munich.
The American, who made the Monte-Carlo semi-finals, came back to clinch a 4-6, 6-3, 6-3 victory against Marton Fucsovics.
"First match, I had to get used to the conditions," Fritz said.
"Everything plays a bit different.It's obviously very cold.I took some time to feel it out and I feel like I just played better as the match kept going."