Former world number one Martina Hingis, due to make her WTA comeback in doubles on Wednesday night, said she isn't considering a singles return.
"Not singles, no," Hingis, 32, said Wednesday, hours before she was to take the court with doubles partner Daniela Hantuchova at the WTA's Southern California Open.
"It's a completely different world. Even World Team Tennis now, it's brutal, it's only one set but still the next day you wake up, and you have to put so much more effort into it."
Hingis, who won five Grand Slam singles titles and nine in doubles and was ranked number one in the world for a total of 209 weeks, said she didn't think she had the appetite for the training that would be necessary.
And having been at the pinnacle of the women's game while still a teenager, she can't see herself putting in necessary work if she's not going to be a contender.
"When you're 17 everything seems so easy, but now I'm almost twice the age," Hingis said. "I wouldn't want to come out and play one or two matches and then lose third round, that's not my type of personality.
"So not at this point, no."
Hingis first retired from tennis at just 22, in 2003, citing injuries.
A comeback bid in 2005 ended in 2007, not before she learned she had tested positive for a metabolite of cocaine and faced a ban, despite protesting her innocence.
In the second stage of her career, Hingis didn't make it past the quarter-finals at a Grand Slam.
Hingis said it was "kind of weird" to be playing only doubles, but she said she thought she was ready after playing World Team Tennis regularly. She helped the Washington Kastles win the WTT league title last week.
"I feel pretty good. We'll see how it goes this summer," she said. "Obviously I wouldn't put myself in this position if I didn't feel like I could compete at this level. It was good enough for World Team Tennis, but for this world is another question."