(Photo credit: Aaron Doster-Imagn Images)

Tenth-seeded American Frances Tiafoe was forced to retire Wednesday due to a lower-back injury down 6-4, 3-1 while facing Denmark's Holger Rune, the No. 7 seed, at the Cincinnati Open in Mason, Ohio.

Tiafoe leapt out to an early lead in the fourth-round match, winning each of the first three games. But he proceeded to lose six of the next seven games, taking a medical break while trailing 4-5 in the first set, then retiring down a break in the second set.

Rune won 90 percent (19 of 21) of his first-serve points in the abbreviated match, finishing with more than twice as many winners (24 to 10) as Tiafoe.

'From 4-4, when I got the break, and at 5-4, when he had the medical timeout, that's when I felt something was not right with him and after, obviously, I could see he was struggling a little bit,' Rune said. 'As the game is, I tried to move him as much as possible. It's never nice to finish a match like this and I wish him the best recovery.'

After play was suspended Tuesday evening due to inclement weather, rain once again caused delays during the Wednesday action.

Although there was a delay of nearly three hours, that didn't seem to slow down top competitors such as No. 1 seed Jannik Sinner of Italy, who defeated France's Adrian Mannarino 6-4, 7-6 (4), and fifth-seeded American Ben Shelton, who disposed of Roberto Bautista-Agut of Spain 7-6 (3), 6-3, around the extended delay.

With his victory Wednesday, Sinner became just the fourth player since 1990 to reach nine consecutive ATP Masters 1000 quarterfinals, joining Roger Federer, Rafael Nadal and Novak Djokovic.

No. 3 Alexander Zverev of Germany needed just one game on Wednesday to defeat No. 27 seed Brandon Nakashima 6-4, 6-4 after their match was suspended Tuesday night. Zverev faces Russian Karen Khachanov on Wednesday evening after his brief action earlier in the day.

No. 23 Felix Auger-Aliassime of Canada defeated France's Benjamin Bonzi 6-4, 6-3 in an hour and 15 minutes on Wednesday to advance to face Sinner for a spot in the semifinals.

In evening action, No. 2 Carlos Alcaraz of Spain cruised past Italian Lucas Nardi 6-1, 6-4 to reach a quarterfinal match vs. No. 9 Andrey Rublev of Russia, a 6-2, 6-3 victor over Argentina's Francisco Comesana.

French qualifier Terence Atmane upset No. 4 Taylor Fritz 3-6, 7-5, 6-3 to secure a spot in the quarterfinals against Rune.

--Field Level Media