Halle - Spanish world No 1 Rafael Nadal suffered a shock second round defeat at the hands of German world No 85 Dustin Brown on the grass courts of Halle on Thursday.
The left-handed Mallorca native, fresh from his ninth French Open title last Sunday, crashed 6-4, 6-1 at the hands of the lanky Brown who is still looking for his first ATP singles' title.
"Difficult to talk about the match, I don't know what to say. I didn't play," said a downcast Nadal following his defeat.
"It can happen on this surface against such a opponent. This match has no value preparing for Wimbledon but the match was negative in all ways.
"Now, I'll leave to Majorca but not sure I will play because I need to rest and then want to fly to Wimbledon Wednesday early morning," he continued.
The 1.96m (6ft 5in) Brown, who has won two doubles titles, picked up the biggest win of his career on the back of 11 aces and a winning first service percentage of 83 per cent.
Nadal, meanwhile, forced just one break point against his opponent, which he failed to convert, while Brown broke three times on his way to victory in just under an hour.
Awaiting Brown in the quarter-finals is compatriot and 2011 Halle champion Philipp Kohlschreiber.
Earlier, Roger Federer got his Wimbledon preparations fully underway, but he looked out of sorts before finally edging Portugal's Joao Sousa 6-7 (8/10), 6-4, 6-2 in a second round tie.
Playing for the first time since losing to Ernests Gulbis in the last 16 of the French Open, the six-time former winner of the German tournament started brightly but was soon on the backfoot against the improving Sousa.
There were no breaks of serve in the first set and it was Sousa who dominated the tie-break clinching it on his fourth set point.
Federer looked frustrated at times, but the match turned on the seventh game of the second set when Sousa's level suddenly dipped allowing the Swiss great to pounce and secure his first break.
From then on it was all Federer with a break of serve in the first game of the deciding set sending him safely on his way into the last eight.
"I struggled a bit on return during a set and half," said Federer. "Afterwards, it was better, more variation on second serve.
"It was slightly frustrating, but important to stay calm. Maybe I got more confidence winning this way than 6-4, 6-4.
"When I came here (Saturday) to start practice it was so-so, but now it's better. For me, it doesn't take a lot of time to get used to the grass."
Third seed Milos Raonic of Canada lost on Wednesday 6-4, 6-4 to German wildcard Peter Gojowczyk.
Federer's opponent in the quarter-finals will be Lu Yen-Hsun of Taiwan, who defeated big-serving Ivo Karlovic of Croatia 7-6 (7/2), 7-6 (7/3).
"I'll try to climb the mountain. Everybody thinks he's favorite. I will try my best and enjoy," Lu said of his chances.
"If I'm 150% and he's 100% I think I'd still lose. Maybe if he is in a bad day. Nothing worse than a 6-0, 6-0!
"I have a lot of respect for Federer, he's an overall tennis player, won everything. We learn from him watching his games."
Results from fourth day of the ATP Halle Open on Thursday (x denotes seeding):
Dustin Brown (GER) bt Rafael Nadal (ESP x1) 6-4, 6-1
Steve Johnson (USA) bt Teimuraz Gabashvili (RUS) W/O
Roger Federer (SUI x2) bt Joao Sousa (POR) 6-7 (8/10), 6-4, 6-2
Lu Yen-Hsun (TPE) bt Ivo Karlovic (CRO) 7-6 (7/2), 7-6 (7/3)