Sorry, a bit off topic, but Novak was asked a few fan questions in an interview at the World Tour Finals and this was one of them:
Q: Tell me a name of the WTA player that you would like to play mixed doubles, but not our players, Ana Ivanovic or Jelena Jankovic.
ND: Ana Ivanovic
Q: But not them...
ND: Only with Ana.
he's secretly in love with her