Fifth seed Alize Cornet advanced to the second round of the Citi Open on Monday after beating German qualifier An-Sophie Mestach 6-3, 6-3 in an hour and 22 minutes.
Cornet, who was playing Mestach for the first time, saved two out of the three break points she faced and broke her opponent four times.
Sixth seed Irina-Camelia Begu also progressed to the next round after defeating Madison Brengle 6-4, 6-0 in 58 minutes.
However, eighth seed Zarina Diyas of Kazakhstan fell at the first hurdle when she retired with an injury in the second set of her clash with Lauren Davis. The American had won the first set 7-5 and was 2-1 up in the second when Diyas pulled out.
American wildcard Louisa Chirico provided the major upset of the day when she downed Heather Watson, making light work of the Briton in a 6-3, 6-0 victory.
Other players to book their places in the second round on Monday were Yulia Putintseva, Monica Niculescu and Irina Falconi.