Serena: Nerves affected second serve
World number one Serena Williams hit the practice court after her US Open second-round win, discontent with her performance.
Serena Williams is not satisfied with her performances, despite advancing to the US Open third round without the loss of a set.
The world number one's latest victim was Kiki Bertens, Williams moving within five wins of an historic Grand Slam with a 7-6 (7-5) 6-3 result on Arthur Ashe Stadium on Wednesday.
Despite centre court proving to be less windy than in the past with the roof structure forming overhead, Williams struggled with her second serve - producing 10 double-faults for the match, including eight in the tight first set.
Williams said nerves contributed to her shaky display on serve - which saw her hit the practice court following the win.
"Until today I was okay with it. I just got a little nervous today," Williams told a news conference, when asked about expectations on her to complete the calendar Slam.
"But I've been doing totally fine. I've been completely relaxed, chill. I've been really, really fine.
"So I'm going to get back into the place that I was and I'll be fine again."
Williams has lost just twice on the WTA Tour this season, but she simply does not settle for the result as the basis of her mood.
"I definitely feel more determined to do better than what I did. I know I can play better, so... it definitely wasn't my happiest of moments," she replied, when asked about her post-match mood.
"I don't think you should be happy with just winning. At least I'm not. Maybe other people can.
"[I'm] always looking to do better. If I don't play well, I'm not going to be happy even if I won."