When the No. 2 player in the world thinks the No. 1 player can't be stopped, then only the No. 1 player can stop the No. 1 player.

Tennis.com reported that second-ranked Petra Kvitova, the only player to defeat Serena Williams on the court this year, thinks that Williams has a legitimate chance to pull off the calendar Grand Slam.

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"Serena, of course we saw how well she's playing," Kvitova said. "I think that she's really big champion. I think she can really make it. I think that every tournament is a little bit different, and I know how Serena really likes to play on the grass, so for sure she gonna be very dangerous. It's nice that somebody playing so well."

The comment is even stranger, considering the fact that Kvitova, not Williams, is the defending champion at Wimbledon. And most everyone knows how Williams' 2014 Wimbledon turned out, as evidenced by the video of her infamous doubles match going viral.

Kvitova defeated a tired Williams 6-2, 6-3 in the semifinals of the Mutua Madrid Open in early May, which is the lone blemish on Serena's 32-1 record this season. Williams did withdraw from two other matches, against Christina McHale in Rome the week following her loss to Kvitova and against Simona Halep in the semifinals of Indian Wells in March.

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Williams became ill during the French Open and labored in her final three matches but still managed to win her second Grand Slam of the Year. Her semifinals opponent, Timea Bacsinszky, defeated Kvitova in the fourth round at Roland Garros.

To hedge her bet about her comments to tennis.com, Kvitova also mentioned other players that she considered dangerous at Wimbledon - along with herself and Williams.

"I think of course still Maria [Sharapova]," said Kvitova, a two-time Wimbledon champion. "We have to count with her. I think Simona [Halep] had a great run last year. I think when she has her form, she really can be dangerous player. Of course I think some other girls who like to play on the grass, [Sabine] Lisicki, with her serve, she can be dangerous, as well. I think it's not just few players, but it's quite a lot and still the tennis, women's tennis is still very open."