Britain's Johanna Konta will play American Sloane Stephens in the Italian Open second round after a straight-sets win over her compatriot Alison Riske.
Konta, 27, took fewer than 90 minutes to defeat Riske 6-4 6-1 in the first round in Rome.
The British number one beat 2017 US Open champion Stephens in Brisbane in January - their only previous meeting.
The Williams sisters, who share five Rome titles between them, could meet in the second round.
Serena, who has won four titles in the Italian capital, plays Sweden's Rebecca Peterson while 1999 winner Venus Williams faces Belgium's Elise Mertens.