![With Serena Williams entering the twilight of her astonishing career, could Madison Keys be the next American female to hit the world No. 1 ranking and challenge for grand slam titles?](https://media.cnn.com/api/v1/images/stellar/prod/161107161245-williams-keys-gal-3-tease.jpg?q=w_3564,h_2376,x_0,y_0,c_fill/h_447)
With Serena Williams entering the twilight of her astonishing career, could Madison Keys be the next American female to hit the world No. 1 ranking and challenge for grand slam titles?
![Serena herself thinks so. After meeting Keys for the first time in the Australian Open semifinals of 2015, which she won in straight sets, the 35-year-old said of her opponent 14 years her junior: "It was an honor for me to play someone who will be No. 1 in the future."](https://media.cnn.com/api/v1/images/stellar/prod/161107161228-williams-keys-gal-1.jpg?q=w_3600,h_2338,x_0,y_0,c_fill/h_447)
Serena herself thinks so. After meeting Keys for the first time in the Australian Open semifinals of 2015, which she won in straight sets, the 35-year-old said of her opponent 14 years her junior: "It was an honor for me to play someone who will be No. 1 in the future."
![Keys has faced Serena Williams three times and is yet to beat her, but isn't the first player to find overcoming one of the game's greatest ever players an impossible challenge sometimes.](https://media.cnn.com/api/v1/images/stellar/prod/161107161241-williams-keys-gal-2.jpg?q=w_4928,h_3280,x_0,y_0,c_fill/h_447)
Keys has faced Serena Williams three times and is yet to beat her, but isn't the first player to find overcoming one of the game's greatest ever players an impossible challenge sometimes.
![Their most recent meeting came in the final of the Italian Open back in May, that Williams also won in straight sets.](https://media.cnn.com/api/v1/images/stellar/prod/161107161251-williams-keys-gal-5.jpg?q=w_3930,h_2778,x_0,y_0,c_fill/h_447)
Their most recent meeting came in the final of the Italian Open back in May, that Williams also won in straight sets.
![Keys has had an impressive 2016, winning her second WTA Tour title, in Eastbourne in June, reaching the season-ending WTA Finals and breaking into the world's top 10. The 21-year-old was the first American woman to do so since Serena in 1999.](https://media.cnn.com/api/v1/images/stellar/prod/161107161253-williams-keys-gal-6.jpg?q=w_3000,h_2000,x_0,y_0,c_fill/h_447)
Keys has had an impressive 2016, winning her second WTA Tour title, in Eastbourne in June, reaching the season-ending WTA Finals and breaking into the world's top 10. The 21-year-old was the first American woman to do so since Serena in 1999.
![Serena needs just more more slam to reach 23 and eclipse the standard set by German legend Steffi Graf back in 1999 with her victory at the French Open.](https://media.cnn.com/api/v1/images/stellar/prod/161107161321-williams-keys-gal-8.jpg?q=w_3072,h_2136,x_0,y_0,c_fill/h_447)
Serena needs just more more slam to reach 23 and eclipse the standard set by German legend Steffi Graf back in 1999 with her victory at the French Open.
![Two legends of the game are backing Serena to get there. Martina Navratilova (L) and Chris Evert -- both of whom can boast 18 grand slam titles -- think Williams has one or two more majors left to win.](https://media.cnn.com/api/v1/images/stellar/prod/161107161317-williams-keys-gal-7.jpg?q=w_5014,h_3342,x_0,y_0,c_fill/h_447)
Two legends of the game are backing Serena to get there. Martina Navratilova (L) and Chris Evert -- both of whom can boast 18 grand slam titles -- think Williams has one or two more majors left to win.
![Both Evert and Navratilova think Wimbledon represents Serena's best chance to hit 23 majors. She has already won seven times at SW19, -- the same as Graf -- and Navratilova told CNN's Open Court show: "If Serena stays healthy it's almost impossible for someone to beat her on the grass."](https://media.cnn.com/api/v1/images/stellar/prod/161107161248-williams-keys-gal-4.jpg?q=w_4456,h_2970,x_0,y_0,c_fill/h_447)
Both Evert and Navratilova think Wimbledon represents Serena's best chance to hit 23 majors. She has already won seven times at SW19, -- the same as Graf -- and Navratilova told CNN's Open Court show: "If Serena stays healthy it's almost impossible for someone to beat her on the grass."