SINGAPORE - New mother Serena Williams will lack some of her trademark intimidation factor when she returns to tennis, US great Chris Evert told AFP, warning that the 23-time Grand Slam-winner may find her comeback tough. Williams, who gave birth to a baby girl in September, has said she's planning to defend her title at the Australian Open in January -- just four-and-a-half months after becoming a mother. But Evert said standards in women's tennis had risen this year since Williams stepped off the tour, warning that the 36-year-old would be returning to a more competitive environment. "I think that this whole year, the level has gone up because Serena hasn't been dominant and the other players have all felt that they had a shot at it, at the number one ranking," Evert said.