Keys overcame seven double faults and saved five break points to secure the first set in 49 minutes. Valentova pushed to stay in it, but Keys ripped a forehand return winner off the 18-year-old’s second serve to break for a 2-0 lead in the second set. From there, she won four of the final five games to close out a hard-earned victory, according to WTA.

"They’re just so young, and they have so much energy, and they’re so excited to be out here. And they’re just so good. So you definitely have to just expect them to play some really great tennis, and like I said, try to lean on experience in those big moments and just kind of hope that that gets you across the finish line," said Keys.

Keys will face another teen sensation, Victoria Mboko, in their first meeting on the WTA Tour. The No. 8 seed Mboko saved two match points against Anna Kalinskaya to reach the second round of the Adelaide International in two hours and 22 minutes.

Earlier, Jaqueline Cristian defeated Daria Kasatkina for the first time, with a second-set bagel. Cristian survived a chaotic first set before running away with a 6-4, 6-0 win in 1 hour and 31 minutes.

This was Cristian's second straight-sets win of the week, following her upset of No.

Earlier, Jaqueline Cristian defeated Daria Kasatkina for the first time, with a second-set bagel. Cristian survived a chaotic first set before running away with a 6-4, 6-0 win in 1 hour and 31 minutes.

Cristian and Birrell have split their two previous meetings, with the Romanian winning a dominant 6-0, 6-1 last year at Roland Garros.

Earlier, Jaqueline Cristian defeated Daria Kasatkina for the first time, with a second-set bagel. Cristian survived a chaotic first set before running away with a 6-4, 6-0 win in 1 hour and 31 minutes.

Cristian and Birrell have split their two previous meetings, with the Romanian winning a dominant 6-0, 6-1 last year at Roland Garros.