Rains washed out the latter part of Wednesday's schedule but before the showers came Isner eliminated Alex Kuznetsov 7-6 (7-2), 7-6 (7-4).
The last six sets Isner has played have all gone to tiebreaks, going back to the final set of his semifinal win in Atlanta last week. He has won five of those six sets and received a bye past the first round of this event.
Mardy Fish also reached the third round Wednesday with a 6-3, 7-5 win over Julien Benneteau and Ivan Dodig advanced with a 2-6, 6-2, 6-3 decision over Tobias Kamke.
Among the matches postponed by the rains was the scheduled meeting between No. 1 seed Juan Martin Del Potro and Ryan Harrison.
Tommy Haas had a 1-0 lead in the third set over Tim Smyczek when the rains came.