Top seed Jack Sock booked his place in the Atlanta Open quarter-finals, while Kyle Edmund also advanced on Thursday.
Sock, who has enjoyed an excellent 2017, was too good for 2014 runner-up Dudi Sela 6-4 6-3 in their last-eight clash, which finished after midnight local time at the ATP 250 event.
Awaiting Sock in the quarter-finals is Edmund after the British fifth seed edged past Peter Gojowczyk 2-6 6-4 7-5.
Ryan Harrison and Christopher Eubanks set up an all-American clash on a rainy day in Georgia.
Fourth seed Harrison battled past Australian John Millman 6-7 (2-7) 7-6 (7-4) 7-5 in two hours, 46 minutes, saving a match point in the second set.
Eubanks, a wildcard, continued his run with a 6-4 4-6 6-2 victory over eighth seed Jared Donaldson.