The semi-finals of the inaugural ATP Dallas Open will feature four Americans, while Australia’s Jordan Thompson was among the losing quarter-finalists.

Seventh-seeded Marcos Giron upended No.1 seed Taylor Fritz – who is also his practice partner – 6-4 3-6 7-6(7-3) on Friday to advance.

In Saturday’s semi-finals, Giron will face fourth seed Jenson Brooksby, who crushed Thompson 6-3 6-0.

The 6-foot-11 Reilly Opelka and 6-foot-10 John Isner will take the game to great heights in the other semi-final, a clash of players seeded second and third respectively.

Dallas resident Isner made quick work of qualifier Vasek Pospisil of Canada, winning 6-4 6-4.

Opelka didn’t waste time, either, beating fifth-seed Adrian Mannarino of France 6-3, 6-1.

Having four Americans in the semis is rare; the last time it happened at an ATP event was in 2004 in San Jose, California.

Giron battled back after losing the second set and falling behind 4-2 in the third set.

“When I was down a break in the third, we got a change of balls, and I was able to kind of take advantage of that,” Giron said. “Once I was able to sneak out a break, my level improved.”

By defeating the 19th-ranked player in the world, No. 70 Giron scored his fifth career win in 18 chances against top 20 players to reach his second ATP semifinal.

Fritz was playing in his first tournament as the top seed.

“I’ve practiced with Fritz so much,” Giron said. “We’re both based in LA and we both train in Carson (California) so we know each other’s game well.”