SINGAPORE - The only thing that can stand in the way of Serena Williams winning her 22nd Grand Slam title at the Australian Open is the player herself, says 2013 Wimbledon champion Marion Bartoli.

The retired Frenchwoman told regional media on Friday morning that the strength of the weapons in the world No. 1's arsenal makes her almost unbeatable now. Williams is scheduled to meet Germany's Angelique Kerber in thewomen's singles final on Saturday evening.

Said Bartoli, a pundit for FOX Sports Asia, in a phone interview from Melbourne: "Serena needs to be able to make the shots that are way too big for any opponent in the world now - her serve and her return of serve. If she stays calm and does that, I don't see one player in the world that can beat her."

Williams has a 5-1 head-to-head record against No. 6 Kerber, a first-time Grand Slam finalist. Kerber last beat the American in Cincinnati in 2012.

Bartoli, 31, herself has tasted success in beating Williams in a Grand Slam when she was victorious at the 2011 Wimbledon. She added: "Serena is all about her stress level. We saw it when she played Agnieszka Radwanska (in the semi-final on Thursday). She dominated and sometimes got a little stressed and she starts to miss.

"When she gets nervous she gets slower in her footwork and her unforced errors skyrockets and makes it possible for her opponents to come back in a match.

"Serena is able to just take matches completely off you. You feel like you can't play, can't get into rallies against her."