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. My actual tennis I think I could play a lot better,” Williams said. 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.