CINCINNATI, OH, USA - Maria Sakkari's summer surge continued at the Western & Southern Open on Tuesday, saving three set points in the second set to dispatch BNP Paribas Open champion Naomi Osaka, 6-3, 7-6(8), earning her fifth Top 20 win of the season.

"I think I played a great match, two great sets," Sakkari said after the match. "I think I was serving really well and I came up with good serves during her set points. There were good rallies; I tried to be solid. She's obviously very aggressive but my defensive game is quite good."

Sakkari first served notice on the red clay of the Internazionali BNL d'Italia where she scored back-to-back upsets over Kiki Bertens and Karolina Pliskova, and backed up her maiden WTA runner-up finish at the Mubadala Silicon Valley Classic in emphatic style against Osaka, advancing in one hour and 49 minutes on Grandstand court.

"I have a clear idea of what I have to do on court now. If I could do it every single match, that'd be great, but I'm trying to do it more consistently. The serve has to be quite big on my side, but I'm more used to the level after playing all the top girls. Some of them I've played twice or three times, like Naomi or the Williams sisters. That helps."

Osaka was on top of the world at the Indian Wells Tennis Garden, where she rode an eight-match winning streak into her first title and a stunning win over 23-time Grand Slam champion Serena Williams at the Miami Open.

Since reaching the third round of Wimbledon, the Japanese 20-year-old is still finding her rhythm on hardcourts after early losses at the Citi Open and Coupe Rogers.

The Greek youngster, up to a career-high ranking of No.31, scored the first break of the opening set, and held off Osaka in a marathon eighth game that forced her to save three break points before breaking serve once more to get within one set of victory.

The second set was a far more contentious affair, with Sakkari and Osaka traded 12 straight service holds. Sakkari earned a pair of match points as the World No.19 served at 4-5, but Osaka saved both to ensure a tie-break.

An ill-timed double fault from Sakkari handed the mini-break back to Osaka, who served her way to three set points as the sudden death reached its critical phase. Sakkari saved all three and flipped the script to convert her third match point.

In all, Sakkari struck an impressive 26 winners to 30 unforced errors in two sets. Osaka showed off her signature power on 15 winners but struggled for consistency with 29 unforced errors, and couldn't dent the Sakkari serve with an 0 for 2 break point conversation rate.

Up next for the 23-year-old is another young gun in Estonia's Anett Kontaveit, who eased past former Wimbledon quarterfinalist Barbora Strycova on Monday.

"We've played this year, and have played so many times, so we know each other well. She's a great player, and it'll be a tough match. I haven't thought about it yet."