South African eighth-seed Lloyd Harris was bundled out by Australian Jordan Thompson 7-6 (7-2) 1-6 6-2 in a seesawing contest.
Thompson, who is ranked 63rd in the world, got the better of Harris, showing to grit to win in two hours and 30 minutes.
In the final match of the day, play was suspended due to rain and lightning after the first set with American Sam Querrey leading 6-4 against German Peter Gojowczyk.
Former world number 11 Querrey sent down 12 aces in the first set before the weather intervened.
The winner of Querrey and Gojowczyk will take on Thompson.
Steve Johnson defeated Alexei Popyrin 7-6 (7-4) 6-3, while Bjorn Fratangelo beat Italian Andreas Seppi 7-5 7-6 (7-5).