DELRAY BEACH, Fla. (AP) -- Australian qualifier Marinko Matosevic beat No. 6 seed Alex Bogomolov Jr. of Russia 4-6, 6-1, 6-3 Wednesday to reach his first career ATP quarterfinal at the Delray Beach International Tennis Championships.
The 173rd-ranked Matosevic had 11 aces and won five of eight break points.
Bogomolov had the best season of his career in 2011, starting the year at No. 166 and finishing at No. 34. Fellow players voted him the year's most improved player.
Gulbis beat Steve Darcis of Belgium 6-7 (6), 6-1, 6-3 to reach his first quarterfinal of the season. The Latvian won 40 of 45 points on his first serve and fired 10 aces.
Top seed John Isner meets fellow American Ryan Sweeting on Wednesday night. Eighth seed Bernard Tomic of Australia will take on American qualifier Tim Smyczek in the second night match.