JOIN USArgentine Juan Martin del Potro maintained his perfect career record against Dominic Thiem on Thursday with a popular 6-2, 7-6 (7) victory over the Austrian in their Acapulco Open quarterfinal in Mexico.
The former U S Open champion raced through the first set against the world number six but had to battle much harder to secure the win in a tight second stanza on the outdoor blue hardcourt.
The victory came in the tiebreak on a Thiem double fault, which was confirmed after the third seed, with nothing to lose, challenged the call.
Hawkeye revealed the ball had been a few millimetres long, sending the enthusiastic pro-del Potro crowd into wild cheering and applause.
Del Potro, who improved his head-to-head record against Thiem to 4-0, will have little time to savour his victory as he prepares for Friday's semifinal against second seed Alexander Zverev.
German Zverev earlier dusted American Ryan Harrison 6-4, 6-1.
Kevin Anderson also reached the last four after serving 18 aces and saving six break points to edge South Korean young gun Chung Hyeon 7-6 (5), 6-4 in a quarterfinal.
Standing in the South African's path to the final will be 21-year-old unseeded American Jared Donaldson, who won 100 percent of his first serve points in a 6-3, 6-1 thrashing of Spaniard Feliciano Lopez.
Agut in semis
Third seed Roberto Bautista Agut powered past Croatia's Borna Coric 7-6 (4), 6-4 to reach the semifinal of the Dubai Duty Free Tennis Championships on Thursday.
Bautista Agut overcame a slow start to outclass his opponent and stay in the hunt for his second title of the season.
The Auckland Classic champion takes on wildcard Malek Jaziri for a place in the final. Jaziri defeated Stefanos Tsitsipas 6-4, 3-6, 6-3.
Bautista Agut, who trailed 1-3 early in the contest, fought back to claim the opening set in the tiebreak. He then won a decisive break at 4-4 in the second set and pushed on to reach his first Dubai semifinal.
Jaziri recovered from losing the second set to pull away to reach his third semifinal on the Tour.
"It's a great feeling," Tunisian Jaziri said. "I am playing the best tennis of my life."
Second seed Lucas Pouille battled back after losing the first set to Japan's Yuichi Sugita to win 3-6, 6-3, 6-2. The Frenchman takes on the winner of the match between Filip Krajinovic and Evgeny Donskoy.