Updated

Two-time Grand Slam singles champion Svetlana Kuznetsova defeated Irina-Camelia Begu of Romania 6-1, 6-4 Sunday in the first round of the Sydney International tennis tournament.

Defending champion Kuznetsova broke the Romanian's serve in the ninth game of the second set, then held serve to advance to the second round of the ATP-WTA tournament.

The Sydney International is one of several Australian Open Series warmup events ahead of the first Grand Slam of the year beginning in Melbourne on Jan. 16.

Earlier, Brisbane International finalists Karolina Pliskova and Alize Cornet withdrew from their next scheduled tournaments due to injuries.

Pliskova, who beat Cornet 6-0, 6-3 at Brisbane on Saturday evening, withdrew from the Sydney International with a left inner thigh injury. Pliskova, who would have been seeded fourth in Sydney, was replaced by lucky loser Roberta Vinci of Italy.

Sydney officials also announced seventh-seed Elina Svitolina of Ukraine withdrew due to a viral illness.

"I've had constant headaches for the last two days and unfortunately in today's hot weather it got even worse when I was warming up and my body wasn't ready to compete," Svitolina said.

Svitolina was scheduled to play Olympic champion Monica Puig on Sunday, but Puig will now play a lucky loser from qualifying on Monday.

At Hobart, defending champion Cornet withdrew from the tournament with a back injury, a Tennis Australia official said. American Shelby Rogers posted the first upset of the tournament in the opening match, beating second-seeded Anastasija Sevastova of Latvia 6-2, 1-6, 6-4.

In a men's tournament at Auckland, New Zealand, top-seeded Roberto Bautista Agut and second-seeded John Isner headline the entries.

Bautista Agut, Isner, third-seeded David Ferrer and No. 4-seeded Jack Sock have first-round byes in the tournament which begins Monday.