The 18-year-old Russian showed some nice moments throughout the match but found her Romanian opponent just too consistent for her.
Playing in her first main draw outside of Russia, Rybakina, who had beaten Andrea Gamiz in the opening round, got off to an inauspicious start as she was broken in the opening game of the match but immediately responded with some well-constructed points to hit back.
She had shown several moments of quality in the formative stages, including a deft drop to nudge ahead in the third game, but Buzarnescu’s play was more pragmatic and more consistent.
Indeed, double faults from the Russian, who made 40 unforced errors, played a big role in the 30-year-old breaking twice midway through the set to engineer a commanding 5-2 advantage.
Rybakina did succeed in getting one of those back but again showed her inconsistency to be broken for a fourth time having been 30-0 up. Again, a couple fault when facing break point was her downfall.
When Buzarnescu showed efficiency to break in the second game of the second set, there was a sense that she might begin to run away with the match, but her opponent constructed a handful of nice points to offer a quick reply. Indeed, it was the Romanian’s second serve this time that was found wanting.
The players exchanged service holds all the way through to 5-4 without any particular concerns. Rybakina fashioned a half chance in the ninth game, moving 15-30 up, but was unable to get even to deuce.
Asked to serve to save the match, the youngster was able to hold her nerve under pressure twice, even saving a match point in the 12th game of the set before two powerful strikes saw he reach a tiebreak.
In that extra game, however, Buzarnescu took charge, winning the first six points as her opponent's radar finally failed her. She finally sealed the match on her fourth opportunity.
Su-Wei Hsieh, the No.8 seed, or Lucia Safarova await in the quarterfinals.