Washington - Britain's Kyle Edmund won nine of the last 10 games to upset US top seed Jack Sock 6-4, 6-1 Friday and reach the ATP BB&T Open semi-finals.
Edmund, a 22-year-old born in South Africa, advanced to his second career ATP semi-final after last year's European Open in Antwerp. He has yet to reach an ATP final.
Sock broke Edmund in the seventh game but the Briton broke back in the eighth and 10th games, capturing the first set in 59 minutes, then took only 29 more to finish off the match.
Blocking the world number 45's path to the championship match of the US Open hardcourt tuneup in Atlanta is American fourth seed Ryan Harrison, who ousted 461st-ranked US wildcard Christopher Eubanks 6-1, 6-2.
Harrison, ranked 42nd, won his only ATP title in February at Memphis without dropping a set. He has never faced Edmund.
Saturday's other semi-final pits third seed Gilles Muller, coming off a Wimbledon quarter-final run and upset of Rafael Nadal, against US second seed John Isner, coming off his first victory in two years last weekend in Newport.
Muller defeated US qualifier Tommy Paul 6-3, 6-1, in a quarter-final. The 34-year-old Luxembourg left-hander blasted 16 aces to oust the 20-year-old world number 291 in only 69 minutes.
Isner, a three-time Atlanta champion, fired 13 aces to oust Slovakia's Lukas Lacko 7-5, 6-4. Lacko's second double fault of the match gave Isner the first break chance of the second set and the American took advantage for a 5-4 lead, then held serve to finish off his 129th-ranked foe after 73 minutes.
Muller downed world number two Nadal in a five-set Wimbledon thriller earlier this month, winning 6-3, 6-4, 3-6, 4-6, 15-13 after four hours and 48 minutes to reach his first Grand Slam last-eight since 2008, falling to Marin Cilic in the quarters.
Muller, ranked a career-high 22nd, seeks his third career ATP title and third title of the year after wins in January at Sydney and last month at Rosmalen.
He lost his first five career ATP finals from 2004 to last July and was also runner-up two months ago at Estoril.
Isner, ranked 20th, won both prior matches against 129th-ranked Lacko, in 2014 at Auckland in and in a 2014 Davis Cup tie.
He owns a 3-2 career record against Muller, including three-set wins in the 2010 second round and 2011 semi-finals at Atlanta plus another in 2012 at Memphis.
Muller won their most recent meetings in the third round of the 2015 Australian Open and the round of 16 last year at Queen's.
Isner, seeking his 12th career title, was a 2010 and 2011 Atlanta runner-up before winning titles in 2013, 2014 and 2015 only to fall to Aussie Nick Kyrgios in the 2016 final.
Gilles Muller (LUX x3) bt Tommy Paul (USA) 6-3, 6-1
John Isner (USA x2) bt Lukas Lacko (SVK) 7-5, 6-4
Ryan Harrison (USA x4) bt Christopher Eubanks (USA) 6-1, 6-2
Kyle Edmund (GBR x5) bt Jack Sock (USA x1) 6-4, 6-1