Fresh off her sixth career title in Brisbane last week, No.1 seed Elena Rybakina extended her winning streak to six matches in the second round of the Adelaide International with a 6-3, 7-5 win over lucky loser Cristina Bucsa.

The World No.3 had to pass her toughest test of the season so far, though. She had only dropped 15 games across her five Brisbane matches combined, and none of her opponents had detained her for longer than 73 minutes. However, Bucsa went toe-to-toe with Rybakina for 1 hour and 30 minutes, and only the former Wimbledon champion's clutch play on important points enabled her to come out on top of a contest that was close to swinging away from her.

"For me it was a bit tough to get used to the conditions, and we're playing late," Rybakina said afterwards. "She played really well today, especially coming forward -- you don't see this much, so it was a bit surprising for me."

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Indeed, Bucsa raced out of the blocks with a clear game plan. The Spaniard was determined to impose herself on the match with quick baseline redirections, drop shots out of nowhere and -- as Rybakina had noted -- superb touch at net.

She played an impeccable first set, tallying nine winners to only three unforced errors, and maintained her positive ratio in the second with 11 more winners to nine unforced errors.

Rybakina was not as sharp off the ground as she had been in Brisbane, tallying 18 unforced errors overall. But her first serve was as formidable as ever, and came to her rescue when she most needed it. Rybakina saved the first seven break points she faced -- including all four in the opener. Conversely, she converted her first two opportunities to capture the Bucsa serve at the end of the first set and the start of the second.

But No.61-ranked Bucsa, who won her first WTA 125 title in Limoges a month ago, kept pressing, and finally took the Rybakina serve at the seventh time of asking to level for 3-3 in the second set as the Kazakh netted a volley.

The remainder of the match hung in the balance until the end. Rybakina broke Bucsa again at 6-5, but had to save another break point when serving for victory with a backhand winner. On her second match point, she slammed down an 11th ace to set up a quarterfinal meeting with Ekaterina Alexandrova, who defeated No.8 seed Veronika Kudermetova 6-4, 6-4, reprising the result of last year's 's-Hertogenbosch final.

Alexandrova now owns a 3-2 head-to-head advantage over Kudermetova, but this win was her first in the series away from grass.

Meanwhile, last year's runner-up Daria Kasatkina pulled off a remarkable comeback against qualifier Anna Kalinskaya for a 5-7, 6-4, 7-5 victory in 2 hours and 51 minutes. The World No.15 faced a point to go down a set and 5-0, but turned the match around with a run of eight straight games to lead 2-0 in the decider.

Highlights: Kasatkina def. Kalinskaya

Kalinskaya mounted one last charge from 5-3 down in the third set, saving two match points to level at 5-5. But Kasatkina stayed resilient, sealing her fourth win in five meetings with Kalinskaya after the latter double faulted facing a third match point.