New mother Serena Williams will lack some of her trademark intimidation factor when she returns to tennis, US great Chris Evert said, warning that the 23-time Grand Slam-winner may find her comeback tough.

Serena Williams and (inset) Chris Evert
Serena Williams and (inset) Chris Evert

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.

"There's so many things we don't know about Serena, how it's going to feel to her being a mother coming back, is it going to distract her, is it going to motivate her more?" Evert said.