Isner lost to Albot last week in the first round of the New York Open, and had lost in the opening match of his three previous tournaments this year.
No. 2 Juan Martin del Potro broke serve four times to beat Jeremy Chardy 6-2, 6-4. No. 9 Milos Raonic, last year's runner-up to champion Jack Sock, swept the final five games and beat Taro Daniel 6-1, 7-5.