Her superior serve back at its unreturnable best, Serena Williams was in full control of her French Open match - until, suddenly, that stroke wasn't as dominant and neither was she.
And then, pushed to a third set by an opponent offering up all sorts of spins and speeds and angles, Williams regained her form and forged to the finish.
Williams returned to the third round at Roland Garros, where she has won three of her 23 grand slam singles titles, by beating 174th-ranked Mihaela Buzarnescu 6-3 5-7 6-1 Wednesday on Court Philippe Chatrier.
Her serving, especially at the outset, was much better than in her first-round win.
"I've been practising my serve a lot. I've been playing, in practice, unbelievable on my serve. The other night was, wooooow," she said, rolling her eyes.
"I'm glad it came better today.
"My coach told me it's good that I'm doing it well in practice, because eventually it will be good in the match."
By the end of the first set, Williams had won 20 of 23 points she served.
In the second set, things changed with Buzarnescu finding her rhythm to break serve twice but after a bit of a reset, Williams got going back in the right direction.
"I knew going into the third, I just had to zero in on those important points," she said.
"If I could just take those, it would be an easier time for me."
Last year, Williams withdrew before the second round in Paris because of an injured left achilles.
No such issues so far this time, and the 39-year-old American covered the court well, although she did have some tape on her right thigh.
Next for the seventh-seeded Williams is an all-American match-up against Danielle Collins, who overwhelmed Anhelina Kalinina 6-0 6-2.
Ajla Tomljanovic, the only Aussie woman in action on Wednesday, was beaten 6-2 6-3 by Russia's 31st seed Anastasia Pavlyuchenkova.
Third-seeded Aryna Sabalenka littered the court with dozens of unforced errors but still beat Aliaksandra Sasnovich in their Belarusian battle 7-5 6-3 to move into the third round.
The upsets resulted in 10th-seeded Belinda Bencic and Veronika Kudermetov, the 29th seed, going out while other seeded players to advance to the last 32 were Victoria Azarenka, Marketa Vondrousova, Elena Rybakina, Madison Keys and Anastasia Pavlyuchenkova.