Kei Nishikori rallied past Radu Albot to book his spot in the New York Open semi-finals, while Sam Querrey also reached the last four.
Back on the ATP World Tour after building up his fitness on the Challenger Tour - having missed the Australian Open and the end of the 2017 season - Nishikori stayed hot with a hard-fought 4-6 6-3 6-1 win on Friday.
Nishikori was broken three times by Albot in the opening set but the Japanese star composed himself, only facing one break point for the remainder of the match as he earned a showdown with top seed Kevin Anderson.
Anderson - last year's US Open runner-up - outlasted talented American Frances Tiafoe 6-3 5-7 6-4.
Tiafoe was making his Tour-level quarter-final debut, and while he levelled the match to force a deciding set, he was unable to upstage the South African.
American second seed Querrey will face Adrian Mannarino in the other semi-final thanks to his 7-6 (7-5) 7-6 (7-4) victory against big-serving Croatian Ivo Karlovic.
"I couldn't have served much better," said Querrey. "I don't even know if we went to deuce, and I had good rhythm on my serve, and that's what freed me up a little bit in the tie-breaks."
Mannarino - the fourth seed - prevailed 7-5 2-6 6-3 against Adrian Menendez-Maceiras.