French qualifier Albano Olivetti stunned Mardy Fish 6-3, 3-6, 6-3 in the second round of the Open 13 on Thursday.
The second-seeded American rallied from a 3-1 deficit in the second set to level the match. But the 388th-ranked Olivetti jumped out to a 3-0 lead in the decider and kept his composure to earn the biggest victory of his young career.
Olivetti served 23 aces and will meet Michael Llodra in an all-French quarterfinal. Llodra downed sixth-seeded Alexandr Dolgopolov of Ukraine 6-4, 5-7, 7-6 (5).
Llodra had 19 aces, and the 2010 champion won four straight points to take a 5-2 lead in the deciding tiebreaker.
Juan Martin Del Potro also advanced to the quarterfinals when a right foot injury forced Nikolay Davydenko of Russia to retire with the match level at one set apiece.
The fourth-seeded Argentine lost the opening set 7-6 (6) but took the second 6-4 when Davydenko said he couldn't continue.
"It was a really tough match," Del Potro said. "But I'm glad to go through. Unfortunately, he can't finish the match. And I wish him a fast recovery for the next tournament."
Davydenko put Del Potro under pressure in the first set by winning 10 of 12 points at the net. He saved four set points and hit 22 winners to 14 for the 2009 US Open champion.
Del Potro fought back in the second set, breaking for a 4-3 lead when Davydenko double-faulted. He served his 16th ace to close it out.
He will next face Richard Gasquet, who cruised past Igor Kunitsyn of Russia 6-3, 6-2.
The fifth-seeded Frenchman broke Kunitsyn's serve three times and saved all six break points he faced. Gasquet has now reached the quarterfinals four times this season.
"Here I have a really difficult draw," Del Potro said. "It doesn't look like a 250 tournament because the tournament has four top-10 (players). That means this tournament is very important and very high level."
Del Potro paid tribute to the victims of Wednesday's train crash in Buenos Aires by wearing a black ribbon on his T-shirt. Fifty people died when the train crashed at a downtown station.