Andrea Petkovic believes Steffi Graf could defeat Serena Williams in her prime using one weapon in her arsenal

Although Serena Williams is widely considered as the greatest female tennis player of all time, retired German tennis star Andrea Petkovic believes compatriot Steffi Graf would get the best of the American during her prime.

Williams and Graf are tied at one win apiece when facing each other on the WTA tour, with both women facing each other in 1999 when Graf was winding down her career and Williams was just breaking onto the scene. Graf would end her career with 22 Grand Slam singles titles, while Williams would go one step further by having 23 Major singles titles when she retired.

In an appearance on the Rennae Stubbs podcast, Petkovic stated she believes Graf could defeat Williams if both ladies clashed in their primes. The former World No.9 speculated that current World No.1 Aryna Sabalenka had a shot at dethroning Williams, but was certain Graf would get the job done.

"The only player I think could have beaten her (Serena Williams) at her peak, if I had to bet, I would always put my $100 on Aryna," said Petkovic. "But I do think on a random day, Steffi Graf could have beaten her, just because of the slice, where Serena would be bothered by disruption of rhythm however, because she lost to Vinci that year."

Graf's signature slice was used with devastating effect during the German's best years on tour, and Petkovic was of the opinion that her compatriot would use it to trouble Williams. The retired American star fell to Italian Roberta Vinci in the 2015 US Open semifinal, mostly due to Vinci's effective use of the slice.