Croat Mario Ancic battled to a thrilling three-set victory over fifth-seeded American James Blake on Thursday to reach the Hamburg Masters quarter-finals.
The Split-born number 12 seed won 4-6, 7-5, 7-6 to join David Ferrer in the last eight after the Spaniard ground out a 6-2, 6-4 win over compatriot and former world number one Juan Carlos Ferrero.
Fernando Verdasco also made it through to the quarters, the Madrid-born lefthander coming from a set down to upset number seven seed Fernando Gonzalez of Chile, and will face Argentina's Jose Acasuso.
In Friday's other quarter-finals, Max Mirnyi of Belarus plays the Czech Republic's Radek Stepanek, Nikolay Davydenko of Russia awaits Ancic and Ferrer will take on compatriot and number eight seed Tommy Robredo.
Blake served for the match at 5-4 in the final set against Ancic, but the towering Croat broke back and won the tiebreak with a forehand winner down the line having served a crucial 10 aces during the tie.
"It was really aggressive tennis from both of us and you could see a lot of winners, a lot of great points, a lot of coming to the net, a lot of great passes," Ancic said.
"In such an unbelievable match with both guys playing great it comes down to one or two balls and today it was my serve I think that decided it."
Ancic has a tough match in store in the next round against Davydenko, at number four the highest seed left in the draw.
The Ukrainian-born former French Open semi-finalist had little trouble seeing off 13th seed Jarkko Nieminen of Finland on Thursday, winning 6-1, 6-3 in less than an hour.
AMAZING MATCHES
Blake said it had been tough trying to cope with Ancic's formidable serve.
"If he is serving that well, there's not much I can do about it. I'm getting tired of losing amazing matches but hopefully I will win a few soon."
Ferrer earlier came out on top in a closely-fought contest with Ferrero in chilly conditions on the slow red clay of centre court at the Am Rothenbaum.
The 16th seed also triumphed over Ferrero in Monte Carlo last month and maintained his hold over the 26-year-old former French Open champion.
"It was pretty difficult, even if the result doesn't really show it," Ferrer said.
Number 15 seeded Czech Stepanek reached the last eight by defeating Sweden's Robin Soederling 6-3, 6-2 and will play Mirnyi. The giant Belarussian went through 6-3, 6-2 against Frenchman Gilles Simon, conqueror of 2004 French Open champion Gaston Gaudio of Argentina on Wednesday.