Joachim Johansson stunned top seed Rafael Nadal in round two of the Stockholm Open on Wednesday.
Johansson won a Futures event in Sweden last month
The Swede, ranked down at 690 after desperate injury problems, won 6-4 7-6 (7-4) for his first ATP Tour victory since Wimbledon 2005.
A former world number nine, Johansson was playing only his third senior match in that time having spent most of this year on the Challenger circuit.
Earlier, second seed James Blake beat Sweden's Thomas Johansson 6-3 6-2.
The American arrived in Sweden on the back of winning the Bangkok Open.
He has a chance to win this event if he plays like this
"You're never sure if your momentum is going to continue in a new city," said Blake. "It's a great feeling, I hope it continues throughout the week."
Blake will next face sixth seed Olivier Rochus, who beat Paradorn Srichaphan 6-2 6-7 (5-7) 6-2.
Robin Soderling thrashed fellow Swede Jonas Bjorkman 6-0 6-2.
Joachim Johansson has been sidelined for five months because of right shoulder and elbow injuries.
"It's my greatest win ever," said Johansson, who fired down 17 aces. "I had to play aggressive.
"You can't get involved in long rallies with him - he's so good and patient."
Nadal said: "He played with confidence and without pressure, very aggressively. I did not play a bad match.
"His serve is top five for sure. If he continues playing like this he has the chance to make the top eight in (next year's) Tennis Masters Cup.
"He has an unbelievable potential with his serve and forehand, and his backhand is not bad either.
"He has a chance to win this event if he plays like this, but it's never the same to play in the second round as in the semi-finals when pressure is there for a player who wants a lot of points."