Russia’s Maria Sharapova was put under pressure in a first-round win over Simona Halep at the China Open on Monday.

Second seed Sharapova’s serve was broken four time by the Romanian world No. 47, but 33 winners against four for Halep helped the Russian to a 7-5, 7-5 victory.

In the second round, Sharapova faces Romanian No. 1 Sorana Cirstea, who knocked out Sweden’s Sofia Arvidsson 6-2, 6-3 earlier Monday.

Former world No. 1 Caroline Wozniacki, seeded 10th, had to dig deep to beat Chanelle Scheepers of South Africa.

The Dane took the first set, dropping the second on a tie-break to surge back in the decider for a 7-5, 6-7(6), 6-2 win.

Wozniacki now faces world No. 38 Hsieh Su-Wei of Taiwan in round two.

Elsewhere, Anastasia Pavlyuchenkova of Russia was retire from food poisioning while 3-0 down in the decider in her first-round encounter against Slovenian qualifier Polona Hercog.

The next opponent for Hercog will Russia’s Ekaterina Makarova, who upset 13th seed Maria Kirilenko in the first round.