Chris Evert says it is 'ridiculous' to compare Serena Williams with any of the greats of past eras.
The 18-time Grand Slam champion, who sits fifth on the all time list of most women's singles titles, explained that players are continually improving - which is why Serena has to be considered the greatest.
"I think it's apples and oranges," Evert said in an interview with CBS Sports.
"The one thing you can say is that Serena [Williams] is the best tennis player that we've seen, but up until my era and Martina's [Navratilova] era, Steffi's [Stefanie Graf] era, that was true as well. The standards get higher and higher."
Williams, who will be going for a record-equalling 24th Grand Slam title at Wimbledon next month, became a mother in September last year.
Evert says will undoubtedly change her outlook on tennis, as it did for her during her playing career.
"I'm sorry, but being a mom, she's in a different emotional place than she has ever been in her life," said Evert, who has three boys.
"Can she compartmentalize all of that and be almost robotic? Will she regain that focus that she's famous for? It's understandable. You soften your edges. That's gonna be the big challenge."