Naomi Osaka saw her most successful run at a Grand Slam end Monday in a straight-sets loss to top seed Simona Halep in the fourth round of the Australian Open.

In a breakout tournament, the Japanese 20-year-old knocked out two seeds on her way to the fourth round, but was no match for the world No. 1 from Romania, who survived four break points in the sixth game of the first set before cruising to a 6-3, 6-2 victory.

Halep, 26, needed just 1 hour, 19 minutes to book a trip to the quarterfinals, winning five break points against the big-serving Osaka, who came into the match without having lost a set.

Osaka ensured her best-ever finish at a Grand Slam by beating Australian 18th seed Ashleigh Barty on Saturday in front of a vocal home crowd at Margaret Court Arena. The victory followed her second-round disposal of 16th-seeded Elena Vesnina of Russia.