John Isner wins rematch against Radu Albot as Del Potro downs Jeremy Chardy at Delray Beach
John Isner gets back at Radu Albot, who won their match in New York just a week ago. AP

DELRAY BEACH, Florida — Sixth-seeded John Isner overcame a slow start Tuesday to win his rematch against Radu Albot in the first round of the Delray Beach Open, 5-7, 6-3, 6-4.

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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