Angelique Kerber was granted an easy passage into the second of the US Open on Monday as Polona Hercog was forced to retire due to illness in the second set of their match.
Australian Open winner Kerber had claimed the first set 6-0 in just 27 minutes under the newly installed roof at Arthur Ashe Stadium, winning each of her service games to love and breaking Hercog three times.
The Slovenian world number 120 lost the first game of the second set before pulling out of the contest in hot, humid conditions in Flushing Meadows.
Speaking on court after the walkover victory, second seed Kerber expressed her disappointment at the misfortune of Hercog, who had her blood pressure taken during a medical timeout prior to pulling out.
"[It's] not the way I would like to finish my match," Kerber said.
"[But I'm] feeling good and looking forward to playing more matches in front of this amazing crowd."
Of the roof, which will prevent the tournament running long due to rain delays, the German said: "It's unbelievable. They did a really good job. You never know how the weather will change."
Kerber is one of three players, along with Agnieszka Radwanska and Garbine Muguruza, aiming to displace Serena Williams as world number one following the final grand slam event of the year.
"I'm really trying to focus on my game, step by step," she said.
"Let's see if the day will come someday. I will try to give my best here, win all the matches and then we will see."
Kerber  bt Hercog 6-0 1-0 [Hercog retired]
Kerber - 8/4
Hercog - 2/11
Kerber - 0
Hercog - 0
BREAK POINTS WON
Kerber - 3/5
Hercog - 0/0
FIRST SERVE PERCENTAGE
Kerber - 50
Hercog - 17
PERCENTAGE POINTS WON ON FIRST/SECOND SERVE
Kerber - 89/89
Hercog - 41/0
Kerber - 30
Hercog - 9