Fish, a former world No. 7, needed three sets to get past Donskoy 6-3, 3-6, 6-1 at Wake Forest University.
Also moving on to the second round was Yen-Hsun Lu, who rolled over wild card Romain Bogaerts 6-1, 6-1, and Dutchman Robin Haase, who bested Frenchman Adrian Mannarino, 6-3, 6-3.
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