Note that the current Top 4 all hold a Grand Slam title at the moment:
Halep, 2018 RG
Wozniacki, 2018 AO
Muguruza, 2017 WB
Stephens, 2017 USO
Last time this happened was *TWENTY* years ago in Sep 1998: Hingis (AO), Davenport (USO), Novotna (WB) and Sanchez Vicario (RG)
#RG18