WASHINGTON (AFP) - Top-ranked Serena Williams, coming off her fourth consecutive Grand Slam triumph at Wimbledon, said Thursday she has plenty of room to improve before chasing more history at the US Open.
Speaking on a teleconference to promote her first hardcourt tuneup event for the Flushing Meadows fortnight, the 33-year-old American praised her mental game but added that her best is yet to come.
"I'm playing some of my best mental tennis. My actual tennis I think I could play a lot better," Williams said.
"That's really exciting going into 2016."
Before Williams takes a serious look at next year, she will focus on the next few weeks at the year's final Grand Slam event, where she could become only the fourth woman to complete a calendar-year Grand Slam and match Steffi Graf's Open Era record of 22 women's Grand Slam singles crowns.
"I'm not thinking about it much," Williams said of the history within her reach, instead taking pride in what she has already done - win four Slams in a row for the second time in her career, the first such run concluded by a 2003 Australian Open victory.
"I was really excited to achieve that Serena Slam," Williams said.
"It was really important for me to do that. Just holding all four trophies at the same time, two times in one career, I'm not sure how many times that has been done. That really means a lot."
Williams, who was forced out of the Swedish Open with a right elbow injury earlier this month, says she and her game are fine now.
"I feel okay," Williams said. "I always have a little nerves and a little trepidation.
"I feel okay about my game. I'm always looking to improve. I'm never too comfortable. That's when I think you are susceptible to losing."
Williams will return to hardcourts at the WTA Rogers Cup in Toronto in two weeks. Williams won the Canadian crown in 2011 and 2013, the past two times it was staged in Toronto.
"I haven't played on the hardcourt in a while," Williams said.
"It will be a good opportunity to get some matches under me before the US Open."
Asked if her success becomes more gratifying as she gets older, the woman who won her first Slam crown at age 17 at the 1999 US Open said it feels that way at any age.
"I've definitely gotten a little better," she said. "Is it more gratifying? I feel like it's gratifying at whatever age, 20, 18, 16, 6 or 80 or 20.
"I really don't feel I act my age."