Raonic, Young advance to Washington semis
Donald Young of the United States celebrates his win over Kevin Anderson of South Africia during the Citi Open at the William H.G. FitzGerald Tennis Center on August 1, 2014 in Washington, DC - by Rob Carr
Canadian second seed Raonic fired 16 aces with only a pair of double faults to defeat American Steve Johnson 7-6 (7/2), 6-2 while Young, on his best run in three years, outlasted South African seventh seed Kevin Anderson 3-6, 7-6 (7/3), 6-2.
Later quarter-finals at the $1.9 million (1.4 million euro) hardcourt event send Japanese fourth seed Kei Nishikori against French sixth seed Richard Gasquet and Canada's Vasek Pospisil, who upset Czech top seed Tomas Berdych, against Colombia's Santiago Giraldo.
Raonic took only 79 minutes to book his third semi-final appearance of the year after Rome, where he lost to top-ranked Novak Djokovic, and Wimbledon, where he fell last month to 17-time Grand Slam winner Roger Federer.
Young's four-match win streak is his deepest main-draw run since reaching his only ATP final in 2011 at Bangkok, where he lost to Britain's Andy Murray.
"I'm just believing a little more. I'm staying in the matches more, not tapping out," Young said. "I'm still fighting and able to hang in there."
Anderson, who at 21st in the rankings was 52 spots higher than Young, had won all four prior ATP matches with the 25-year-old left-hander and had not been broken this week, a test of Young's new resilient attitude.
"I've been negative before and that hasn't worked," Young said. "Top players in the world stay positive and that's what I want to be. It's just starting to click in."
Japan's Kurumi Nara defeated France's Kristina Mladenovic 6-3, 6-1 to reach a semi-final against New Zealand's Marina Erakovic, who beat Serbian Bojana Jovanovski 6-4, 6-4.
Nara, 22, is ranked 40th, two spots below her career high from last month. She won her first WTA title in February at Rio de Janeiro after reaching her first semi-final last year at Osaka.
Erakovic, 26, is ranked 82nd and on her best run since a runner-up effort at Quebec last September. She won her only WTA title last year at Memphis.
Sixth seed Svetlana Kuznetsova, the 2004 US Open and 2009 French Open champion, won by walkover when American Vania King withdrew with a right hip injury suffered in a second-round victory over Christina McHale.
"After the first set I started to feel some pain," King said. "It began to feel progressively worse. I was hoping it would settle down but this morning I wasn't able to play.
"I don't need a couple of months off. I don't need surgery. I'm going to take a couple days off and go from there."
Russia's Kuznetsova, who made her first WTA final since 2011 just four months ago at Oeiras, has a semi-final date with Russian second seed Ekaterina Makarova, who ousted fifth-seeded compatriot Anastasia Pavlyuchenkova 7-6 (7/3), 6-3.