Top seed Borna Coric advanced to his third semi-final of the year after waiting out a four-hour thunderstorm delay before taking the court against 21-year-old Juan Manuel Cerundolo Thursday night in Winston-Salem.

The storm, initially with heavy rain and later with thunder and lightning, pushed back the start of the night session to around 10.30 pm, leaving officials with no option but to play the two remaining quarter-finals concurrently on Stadium and Court 2.

Coric claimed an early break in the first set against the left-handed World No. 100, who had just three tour-level wins this season coming into the tournament, and pushed on to a 6-3, 6-1 victory.

"I was serving really well and I was much happier with my return today," said Coric. "Even though we had to wait four hours I wanted to play the match tonight so now I get to rest rather than playing two times tomorrow."

The Croatian is chasing his fourth career title and first since he claimed the biggest title of his career just over a year ago at the ATP Masters 1000 tournament in Cincinnati.

In Friday’s Saturday night semi-final, Coric faces a first-time Lexus ATP Head2Head meeting with Argentine Sebastian Baez, who is on the cusp of his second consecutive final after defeating Laslo Djere 6-3, 6-0.

Making his first appearance since winning the Kitzbuehel title on clay, the sixth seed came up clutch in the first set, rallying from 0/40 in the opening game of the match and ultimately saving all five break points he faced in the set.

Baez, who is up to No. 35 in the Pepperstone ATP Live Race, is chasing his fourth career title.

"The first set was difficult for both of us but I tried to be focussed for every point," Baez said. "He's a very good player so I'm very happy to be through to the semi-finals.

"In Argentina I practised two weeks before this tournament and was with my family and my friends, which has given me confidence for this tournament."

Coric and Baez will also play in the first round of the US Open.