Isner lost to Albot last week in the first round of the New York Open, and had been beaten 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.
Ivo Karlovic, the 2015 champion, converted only one of 12 break-point chances and lost to Denis Shapovalov 7-5, 7-6 (4).
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