The two become the latest tennis players to pose for the yearly issue.
The two Americans each claimed their first career WTA titles last week.
The 32-year-old world No. 2 is a spokeswoman for the Pink Ribbon campaign.
The two had been working together since January, and played four tournaments as doubles partners.
An assortment of wild, woolly points from the first five and a half months of the 2014 tennis season.
Sabine Lisicki will take the defending champion's ceremonial opening slot at Wimbledon, instead of five-time champion Serena Williams.
The Roland Garros quaterfinalist inked her first deal with an off-court sponsor.
