Britain's Tim Henman overcame Spanish 14th seed David Ferrer to reach the third round of the Madrid Masters.
Henman wants a return to the world's top 32
The world number 40, a wild card in Spain, stunned his opponent by racing through the first set to win it 6-1.
Ferrer found his form in the second set, aided by 14 unforced errors from Henman, to win it 6-4 and level.
However, he failed to maintain that momentum as Henman pulled away again to clinch the third set 6-1 despite a slight injury niggle in his right leg.
The former British number one will now play Argentine fourth seed David Nalbandian, who dropped a set to Julien Benneteau of France before winning 6-7 (4-7) 6-2 7-5.
It was a topsy-turvy display from the Briton though, who, after fielding three break points in his opening service game, took advantage of a host of Ferrer errors to win the first set 6-1.
I wasn't as consistent as yesterday but in the first and third sets I was probably even better
The 32-year-old's chip-and-charge game really looked to be firing.
But any thoughts that he would breeze through the second set were ended when Ferrer found his range on some booming passing shots to take a 3-0 lead.
Henman broke back to love when the 24-year-old tightened up serving for the set, but Ferrer put that to one side to break back immediately to level.
In a mirror image of the second set, Henman won the first three games of the third despite grimacing with pain as he stretched his right knee out on numerous occasions.
He went on to win despite dropping his serve at 3-0 to seal a deserved, though untidy, victory.
Henman said afterwards: "I wasn't as consistent as yesterday but in the first and third sets I was probably even better.
"So much in tennis is dictated by momentum. It was fantastic, I couldn't be happier.
"I love what I do so there's no question when I've been struggling it can be frustrating, so that's why you really have to enjoy these moments."
Ferrer was left distraught by his performance, saying: "It hasn't been a pity. It's been a whole disaster.
"This has been one of the worst days of my career."