UMAG, Croatia (AP) -- Andreas Seppi of Italy advanced to the quarterfinals of the Croatia Open when Andreas Haider-Mauer retired with an injury while trailing 6-1, 4-0 on Thursday.
Haider-Mauer started well, winning the opening game, but then lost 10 straight games. He sought medical treatment for a lower back injury after the first set and retired in the second.
Horacio Zeballos from Argentina also advanced after rallying to defeat eighth-seeded Carlos Berlocq 3-6, 6-3, 6-2. Tommy Robredo won in straight sets to reach the quarterfinals, defeating Viktor Toricki 6-0, 6-4
Seppi is making his fourth appearance in the quarterfinals at Umag in as many years. He improved to 9-3, with his best result the semifinals in 2009 and 2010 - when he lost both times to Spain's Juan Carlos Ferrero.
Also, Aljaz Bedene defeated fourth-seeded Alexandr Dolgopolov 6-3, 6-1.
Dolgopolov, who won this event in 2011, struggled to keep up. Bedene, currently ranked 100th, won nine out of 10 games after a 2-2 tie in the first set.
Umag will be the second quarterfinal of the year for Bedene, who was a semifinalist in Chennai in the opening week of the season.