Maria Sharapova overcame a sore hamstring, brutal heat and a lack of match practice to reach round four of the Pacific Life Open on Sunday.
The world number one beat France's Nathalie Dechy 7-5 6-2 and next faces number 15 seed Vera Zvonareva.
Third seed Martina Hingis also advanced with a 6-2 6-4 victory over Austria's Yvonne Meusburger.
Sharapova said: "I only started serving five days before the event because I got injured when I landed on serve."
The Russian has hardly played since losing to Serena Williams in the Australian Open final in January.
"That's what I've been practising for and it almost scared me"
"When you don't compete for that amount of time, it's normal," she said.
"In as much as you know you've worked hard and you know you're ready to play, you can't really expect amazing things from your game.
"I definitely feel like these matches are getting the rough stuff out. But it's just good to be back on court and being in some tight situations."
Former world number one Hingis was delighted with her form as she won the first 16 points of the match, playing as well as she has at any time since coming out of retirement 15 months ago.
"The first four games it was unbelievable," she said. "That's what I've been practising for and it almost scared me."
Seventh seed Jelena Jankovic of Serbia beat Martina Muller 6-2 6-4, and eighth seed Anna Chakvetadze of Russia overcame compatriot Maria Kirilenko 6-4 6-1.
Number 11 Shahar Peer of Israel saw off a determined challenge from 19th seed Lucie Safarova of the Czech Republic to win 6-3 1-6 6-4.