Memphis - American John Isner became the latest seed to be upset at the ATP Tour's Memphis Open on Friday as the second seed lost in three sets to Donald Young.
The world No 81 Young posted his first career win over Isner in four meetings by outlasting his fellow American 7-6 (7/5), 3-6, 7-6 (8/6) to reach the semi-finals.
Isner was the last remaining seed in the tournament as none of the top seeds reached the semis.
Young won a first-set tiebreak and dropped the second before holding on in the third set.
He let a triple match point opportunity slip away at 6-3 in the third-set tiebreaker, but after Isner won three straight points to tie it at 6-6, Young won two points to finish off the contest.
Qualifier Mikhail Kukushkin powered his way into the semi-finals with a 6-0, 6-4 victory over fourth-seeded Steve Johnson.
Kukushkin, ranked No 103 in the world, is on a roll. He won three matches while losing only 14 games along the way. This is his first semi-final since 2015 in Sydney, Australia.
Many of the top players in the world decided to skip the Memphis tournament in order to play in events in Rotterdam, Netherlands and Buenos Aires, Argentina.
Kukushkin's semi-final opponent will be Nikoloz Basilashvili, who defeated qualifier Matthew Ebden of Australia 7-6 (7/3), 6-4.
Basilashvili, of Georgia, advanced to the quarter-finals by knocking off top-seeded Ivo Karlovic on Thursday.
Results from Friday at the ATP Tour's Memphis Open (x denotes seed):
Mikhail Kukushkin (KAZ) bt Steve Johnson (USA x4) 6-0, 6-4
Nikoloz Basilashvili (GEO) bt Matthew Ebden (AUS) 7-6 (7/3), 6-4
Donald Young (USA) bt John Isner (USA x2) 7-6 (7/5), 3-6, 7-6 (8/6)
Ryan Harrison (USA) bt Damir Dzumhur (BIH) 6-3, 6-4