NEW YORK—World No. 2 Simona Halep says she isn't surprised that so many top women's seeds have already lost at the U.S. Open because, after eight months on tour, many players are tired out.

Through Tuesday afternoon, No. 6 Lucia Safarova, No. 7 Ana Ivanovic, No. 8 Karolina Pliskova, No. 10 Carla Suarez Navarro, No. 14 Timea Bacsinszky, and No. 21 Jelena Jankovic lost, with No. 3 Maria Sharapova having pulled out before the tournament.  
“I heard about the results. I mean, all the players who lost yesterday, I think they had a great year at the beginning of the year,” Halep said. “So it's tough to stay focused and to stay like 100 percent all the year. I think it's normal.

"Last year I did the same thing. I played very well at the beginning and middle of the year, and then in U.S. and Asia I didn't play so good. So I wasn't surprised. Everyone is fighting like crazy because it's the last Grand Slam. When you play the Grand Slam you have just to give everything you have."

Halep has played very well outside of the Grand Slams this year, winning Indian Wells and reaching finals in Canada and Cincinnati, but has struggled in the majors. She has yet to reach the second week of a Grand Slam tournament this season. In 2014, she reached the final of the French Open, the semifinals of Wimbledon, and the third round of the U.S. Open.

“I'm much better than other Grand Slams,” said Halep, who won her first-round match over Marina Erakovic. “I had this year already two Grand Slams where I lost in first and the second round, everything can happen. You have just to be focused, to do everything you can in that day, because you are not like 100 percent every day. It's impossible. But you have to manage the situation to win the match if you can. The opponent has the chance to win the match and I have a chance to win the match. It's open and I have just to do everything I can there.”