Li Na, who defeated British teenager Heather Watson in the first round of the U.S. Open, says many younger players aren’t mentally strong.

"At least I was 10 years older than her, so I got more experience on the court," the 30-year-old told reporters. "She's play very good, but sometimes I have to show her how good I am. I was like 3-1 down or 5-3 up. If she look me I always been there, so maybe a little bit tough for her. I should used to that against all the young players because they just come to the tournament maybe they think, ‘Oh, she's tough.’ Also girls, they easy to give up in the mind."