Undefeated boxing champ Floyd Mayweather has backed world no. 1 Serena Williams’ attempt to complete the calendar Grand Slam at the US Open in New York. Serena, who is looking for her four-straight US Open title and fifth Grand Slam triumph, will face her sister Venus Williams in the quarterfinal of the season finale tournament.

Mayweather, who will have the final match of his career this weekend against Andre Berto, has thrown his support behind Serena’s journey of achieving a rare feat in the world of tennis. “Money” admitted he wants to see Serena victorious in the US Open and become the first player since 1998 to hold all four major titles in a single year.

"I'm just very proud of her and what she's done during her career,” Mayweather said, reports Sky Sports. “She's done some amazing things in her career.”

“Pretty Boy” also revealed he is proud of what Serena achieved in her tennis career. The 38-year-old Mayweather said he is supporting Serena 100 percent, and suggested that if the 33-year-old Serena could stay focus, she can continue breaking records.

Serena is coming off a third-round win against fellow American Madison Keys in the US Open. Serena defeated Keys in straight sets 6-3 6-3 to book a quarterfinal showdown with her older sister Venus, who cruised into the last eight stage after crushing Anett Kontaveit 6-2 6-1 in only 50 minutes.

Serena said playing with her older sister would be more fun than it used to be since both are trying to win the tournament, with the former gunning for a calendar Slam, while Venus is looking to get her first US Open title since 2001.

“Venus is playing great, I barely had a chance to get ready because she was playing so fast. At least one Williams will be in the semis,” Serena said, The Guardian reported.

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