Polishing the Keys to success

Davenport's teenage protege advances to last 16

Madison Keys, who has been touted as a talented prospect for several years, came of age by beating fourth-seeded Petra Kvitova on Saturday - with former great Lindsay Davenport behind her transformation.

The unseeded American, 19, made her Grand Slam debut at the US Open in 2011 as a 16-year-old and has been steadily climbing the rankings since.