ROME, Italy - Of those on double duty at the Internazionali BNL d'Italia, Naomi Osaka has been the most efficient: her 6-3, 6-3 third-round win over Mihaela Buzarnescu makes the No.1 seed the only player to have won two matches in straight sets today so far.

Having earlier defeated Dominika Cibulkova by an identical 6-3, 6-3, scoreline, the result also puts the Japanese player into her maiden Rome quarterfinal. Prior to this year, Osaka had never made the last eight of any WTA-level clay tournament; 2019 has seen her make at least that stage at each one she has contested, after reaching the Stuttgart semifinals and Madrid quarterfinals already.

The US Open and Australian Open champion was a dominant force on serve over the course of the match, particularly during an opening set in which she conceded a meagre two points behind her delivery. Raining down six aces, including two in a row to seal the set, and even more unreturned serves and one-two punches, Osaka was barely engaged in rallies by an opponent who was only occasionally able to get her returns in play.

Buzarnescu also paid the price for a slow start when she stepped up to the line, sending a forehand long on the second break point she faced to drop serve immediately. Once she had settled, the left-handed Romanian was able to show flashes of the talent that took her into the Top 20 last year, particularly when she was able to make her way forward to put away swing volleys. In the main, though, Buzarnescu would also find herself outgunned from the baseline, held back by both the heaviness and placement of Osaka's groundstrokes.

The 31-year-old was able to get her teeth into the second set to a greater extent, setting the tone by saving three break points to hold in the first game. Though careless errors would cost Buzarnescu her serve in the third game, the San Jose champion would find her best tennis of the day to cling on to the match: lashing her whipped forehand with renewed ferocity, Buzarnescu carved out her first break point of the day with a drive volley - and leveled the score at 3-3 by successfully chasing down a dropshot.

The World No.1, though, was equal to the task. Just as Buzarnescu's shotmaking and angles seemed to have gained the World No.29 the advantage off the ground, Osaka fired a spectacular off forehand winner to carve out a break point for 4-3, duly converted as Buzarnescu sent a backhand just wide.

With Osaka resuming her dominance behind the serve, taking her ace tally to nine and even playing with the confidence to essay some successful finesse with a dropshot-volley combination, the 21-year-old was able to accelerate over the finishing line from there. Storming through eight of the final 10 points of the match, Osaka sealed victory in one hour and 18 minutes to set up a blockbuster quarterfinal against Madrid champion and No.6 seed Kiki Bertens.