Cape Town - Naomi Osaka insists she won't allow herself to become distracted by focusing on retaining the world No 1 ranking, saying she is now just "having fun".
Osaka opened her grass-court season with a hard-fought win over Maria Sakkari in the Birmingham Classic and admitted she has changed her mindset.
The two-time Grand Slam winner has been top of the world rankings since she won the Australian Open, but she has been in poor form since winning in Melbourne.
Several players have had the chance to knock her off top spot since then, but have come up short.
The No 1 ranking is once again on the line at the Nature Valley Classic in Birmingham and French Open champion Ashleigh Barty could take over top spot should things not go well for the Japanese player.
Osaka, who lost in the third round at Roland Garros, was tested by Sakkari in the opening round before grinding out a 6-1, 4-6, 6-3 win in one hour and 59 minutes.
"During my entire clay season, it kind of mattered," the 21-year-old said. "And I think it showed because I was stressed out the entire time.
"So, for me, now, I'm just having fun. I'm enjoying it. And I know that if I play well, then I'll be No 1. But you kind of have to deserve the spot that you're in and if I lose in the first round, I don't deserve to be No 1."
She will take on Yulia Putintseva next after the Kazakh player beat British wildcard Hariet Dart 6-1, 6-4.
Former French Open winner Jelena Ostapenko got a confidence-boosting win as she demolished Iga Swiatek 6-0, 6-2 while Petra Martic beat Ekaterina Alexandrova 6-3, 7-5 win.
Sixth seed Julia Goerges also advanced with 3-6, 6-4, 6-3 win over Dayana Yastremska.