NEW YORK -- Ana Ivanovic kept her hot streak rolling with a straight-set victory to start the U.S. Open.
The eighth-seeded Serb beat American Alison Riske 6-3, 6-0 in the first round Tuesday. Ivanovic has won 48 matches this year, more than anyone else on tour.
The 2008 French Open champion has struggled to get back to that level but finally seems to be inching closer. She returned to the top 10 this month for the first time in more than five years.
"The confidence is on a high level," she said. "I had a great season behind me."
The 24-year-old Riske made a breakthrough at last year's U.S. Open, reaching the fourth round after an upset of Petra Kvitova. She reached a career-high ranking of No. 40 this summer.
Ivanovic was broken in the first game Tuesday but quickly took control. She's won three tournaments this year, tied with Maria Sharapova for second behind Serena Williams.
Ivanovic upset Williams to reach the Australian Open quarterfinals. She was playing well heading to Roland Garros but lost in the third round to Lucie Safarova.
In her last tuneup before coming to New York, Ivanovic beat Sharapova in the semifinals in Cincinnati before losing to Williams in the title match.
Samantha Stosur, the 2011 U.S. Open champ, also quickly dispatched a young American, beating Lauren Davis 6-1, 6-4. The 49th-ranked Davis fell to 0-3 at her home Grand Slam event.
On the men's side, American Sam Querrey improved to 3-9 in five-set matches with a 6-2, 4-6, 6-4, 4-6, 6-3 win over Argentina's Maximo Gonzalez.
Tenth-seeded Kei Nishikori of Japan cruised to a 6-2, 6-4, 6-2 victory over American Wayne Odesnik, showing no apparent effects from a toe injury that hampered his preparations. The 176th-ranked Odesnik earned a wild card into the U.S. Open, his first appearance in five years. He served a yearlong ban after pleading guilty for importing human growth hormone into Australia.
