Serena Williams has kept alive her hopes of a calendar Grand Slam by coming from behind to beat Bethanie Mattek-Sands to reach the fourth round of the US Open.
Vying for the clean sweep of major titles, the world number one shrugged off a 6-3 first-set defeat to win the next two 7-5 and 6-0 to eliminate her fellow American in just under two hours.
Despite being a huge underdog, Mattek-Sands - ranked 101 in the world - looked in the mood for an upset early on as she broke Williams en route to a 3-0 lead in the opener.
The 21-time Grand Slam winner broke back to reduce the arrears to 3-2, but Mattek-Sands was relentless as she returned the favour on her way to a first-set victory.
It acted as a wake-up call for Williams, who found herself under pressure again in the second set but a break of serve helped her into a 5-3 lead, before pulling out another in the 12th game to avoid a tie-break.
From there, Williams went from strength to strength, whitewashing the 30-year-old in the decider to book a date with Keys, whom she beat in the Australian Open semi-final earlier this year.
