"I think that sort of takes a toll on me a little bit because I stress myself out in a way". Osaka faces Latvia's unseeded Anastasija Sevastova in Saturday's semi-finals on Beijing's outdoor hard courts.
The German spit out 31 unforced errors to 16 for her opponent, who notched 6 aces and 93 percent of her first service points overall to seal the win in just over one hour.
The 20-year-old Osaka required a medical break in the second set for what appeared to be lower back pain. Last week, she got to the Pan Pacific Open final in Tokyo.
She was more composed against the Latvian Sevastova, even though she was hindered by her back, which she said was more a case of fatigue than anything more serious. "It's exciting to feel like I'm playing well at the end of the year", world number two Wozniacki said.
Wozniacki is in the hunt for her third title of the year, following her Australian Open triumph in January and her victory at the Eastbourne International in June.
The time off allowed her body to mend and she returned to the sport in January 2015.
Fognini, who was chasing a fourth title of the season, reportedly has an ankle injury.