India's Sania Mirza struggled while Venus Williams barely worked up a sweat, but both women booked their spots on Wednesday in the quarter-finals of the Japan Open.
The second-seeded Mirza had to fight back from a service break down twice in the final set against Casey Dellacqua of Australia before taking the match 6-4, 3-6, 6-4.
The Indian star, said experience proved the difference when it counted, keeping her cool despite losing her serve in the first and fifth games of the decider.
She came back both times to even the score at 2-2 and 3-3, and then took the momentum with two service aces to love for a 4-3 lead.
The 84th-ranked Australian, who looked nervous towards the end, hung in to hold for 4-4, but she hit a forehand long on a break point in the 10th game -- the first match point -- to surrender the quarter-final seat.
"It's about making those balls and making those points when it really counts. Probably she didn't make them the whole match, but I made them at 4-4 and I made them at 5-4. I think that counted at the end," Mirza said.
"In the final set, I played much better than I did in the first couple of sets. I think what's important is that you come through," said Mirza, the world No. 29.
Williams, the reigning Wimbledon champion, had no such trouble with fellow American Vania King, strolling to a 6-0, 6-4 victory.
In the men's singles, 12th seed Thomas Johansson of Sweden, 10th seed Feliciano Lopez of Spain and 16th seed Michael Russell of the United States all safely got past their first matches in Tokyo.
Johansson whipped American Justin Gimelstob 6-4, 6-4, Lopez breezed past another American, Robert Kendrick, 6-2, 6-4, while Russell outplayed Marin Cilic of Croatia 7-6 (7/2), 2-6, 6-1.