Memphis (AFP) - 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 unheralded Donald Young.
The world No. 81 Young posted his first career win over second seed Isner in four meetings by outlasting the 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 semi-finals.
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 seed Steve Johnson.
Many of the top players in the world decided to skip the Memphis Open in order to play in events in the Rotterdam and Buenos Aires tournaments.
Kukushkin's semi-final opponent will be Nikoloz Basilashvili, who defeated qualifier Matthew Ebden of Australia 7-6 (7-3), 6-4.
Georgia's Basilashvili advanced to the quarter-finals by knocking off top seed Ivo Karlovic on Thursday.