Marcos Giron pulled off a big upset by beating top seed Frances Tiafoe 6-1, 6-4 in the quarter-finals of the ATP Dallas Open on Friday. The world number 67 claimed his first victory over a top-20 opponent since he reached the last four in Tokyo in October, where he defeated Felix Auger-Aliassime of Canada.

Giron dominated the match against Tiafoe, who is ranked 14th in the world and had won their last three meetings. Giron did not face a single break point and broke Tiafoe three times to seal the win in just 66 minutes.

Giron will face fourth seed Adrian Mannarino of France in the semi-finals on Saturday. Mannarino advanced after his Australian rival James Duckworth retired due to injury while trailing 2-6, 1-3.

The other semi-final will feature two Americans, second seed Tommy Paul and third seed Ben Shelton. Paul moved closer to his second ATP title by beating Germany's Dominik Koepfer 7-5, 6-3 in a tight contest. Paul and Koepfer exchanged five breaks in the first set, but Paul secured the decisive one in the 11th game and held serve to take the set. Paul wasted four match points in the final game before converting his fifth to wrap up the match.

Shelton overcame a tough challenge from Jordan Thompson, winning 6-7 (2/7), 6-4, 6-4. Shelton lost the first set in a tie-break, but bounced back to break Thompson once in each of the next two sets. Shelton saved four break points in the last game and clinched the match on his second match point.