Australian qualifier Marinko Matosevic upset Russian sixth seed Alex Bogomolov Jr in three sets to reach his first career ATP quarter-final at the Delray Beach International Tennis Championships.

The 173rd-ranked Matosevic fired 11 aces and won five of eight break points in his 4-6 6-1 6-3 victory on Wednesday over the world No.34.

Bogomolov’s peers voted him the most improved player of the year after he rose from No.166 in the world last season.

But Matosevic proved too strong in their second-round clash and next plays Ernests Gulbis for a spot in the last four after the big-serving Latvian beat Belgian Steve Darcis 6-7 (8-6) 6-1 6-3.

Top seed John Isner meets fellow American Ryan Sweeting on Wednesday night before Australian eighth seed Bernard Tomic faces American qualifier Tim Smyczek in the late match.