DELRAY BEACH, Fla. (AP) Yoshihito Nishioka, a 19-year-old from Japan, became the first teenage qualifier to reach the quarterfinals of the Delray Beach Open since his countryman, Kei Nishikori, won the title as an 18-year-old in 2008.
Nishioka advanced Thursday with a 6-1, 6-3 victory over Australian Marinko Matosevic to set up a quarterfinal meeting with Australian Bernard Tomic.
Nishioka's two wins in Delray Beach are the first ATP main draw victories of his career. He qualified at last year's U.S. Open but was forced to retire from his first match against Italian Paolo Lorenzi due to illness.
The Japanese youngster forced Matosevic into long baseline rallies, many with looping forehands that barely clipped the back of the line. He relentlessly chased down every potential ball his opponent hit. After roaring through the first set, Nishioka finally dropped serve in the first game of the second set. But he broke right back on a Matosevic double fault and then broke again for 5-3 when the Australian hit a loose backhand volley long.
''I'm small, so I can't hit bigger,'' the 5-foot-7 Nishioka, who in 2014 became the first Japanese man in 40 years to win a gold medal in singles at the Asian Games. ''Because of that, I can have no unforced errors.''
Like Nishikori, Nishioka moved to the United States just before his 15th birthday to train at the IMG Tennis Academy in Bradenton, Florida, courtesy of the Morita Fund, a scholarship designed to develop Japanese talent. He has practiced with Nishikori, last year's U.S. Open runner-up, and learned by watching him play.
''He's not that big either, but his strokes have control and placement,'' said Nishioka, who first started playing at age 4 at his father's tennis club in Mie, Japan. ''Every time he hits something different, sometimes with spin, sometimes high, sometimes low. I'm learning from him, little by little.''
Tomic slipped by eighth-seeded Viktor Troicki of Serbia 6-3, 6-7 (2-7), 6-4. Troicki and Tomic battled for nearly two hours in 48-degree weather in front of a crowd of barely 200, many cloaked in down jackets and huddled under blankets. Even the players blew on their hands to keep them warm between points.
With the win over his doubles partner, the 46th-ranked Tomic reached his fourth quarterfinal of the season though he has failed to advance beyond that round thus far.
Donald Young reached his third quarterfinal in four ATP events this year with a 6-3, 6-2 win over Alejandro Gonzalez of Colombia.
The 25-year-old American, the No. 1-ranked junior in the world in 2005 who has struggled in the professional ranks, has never before made three quarterfinals in an entire season. In January, he advanced to the quarters in Auckland, New Zealand, and last week he was a semifinalist indoors in Memphis.
Young will play third-seeded Alexandr Dolgopolov for a spot in the semifinals. Dolgopolov beat American Tim Smyczek 6-2, 6-4 to reach his first quarterfinal of the year.
Young and Gonzalez labored through windy conditions that caused the flags atop center court to flap so loudly they sounded like crashing waves. But Young, who hasn't always kept his composure in the past, remained calm throughout the match, even after he double-faulted while serving at set point for the first. Instead of panicking, Young hit a backhand winner on the line and a service winner to clinch the set.
He later served out the match at love.
''The wind was terrible, but it was rough for everyone,'' Young said. ''I like the wind because I hit with a little more spin.''
In 2012, Young struggled through a six-month dry spell in which he lost 17 consecutive matches, the third longest skid in the Open era. He ended that season with a 5-24 record. A year later, he hired a sports psychologist to supplement the coaching he receives from his parents, Donald Sr. and Illona.
''I needed to know why I was losing and my peers were doing better,'' said Young, who still occasionally communicates with the Atlanta-based sports psychologist he declined to name. ''She taught me to focus on the ball and things that I can control. I can just control my mind, what I do on my serve, my competing and my effort.''
Dolgopolov raced to a 5-0 lead in the first set by hitting slice backhands that skittered over the net and deep forehands that forced Smyczek to retreat several feet behind the baseline.
At 4-4 in the second set, Dolgopolov broke when Smyczek had two forehand errors, and he served out the match with an ace and a service winner.