John Isner held off an upset bid by Dudi Sela of Israel on Thursday night to advance to the quarterfinals of the Delray Beach Open after No. 3 seed Kei Nishikori of Japan exited the tournament because of hip flexor injury.

The second-seeded Isner squandered four match points in the third set after leading 4-1, but the 6-foot-10 American rallied from a 5-2 deficit to prevail in the tiebreaker for a 3-6, 6-1, 7-6 (5) victory that earned him a spot in the quarterfinals for the third consecutive year.

He will face American qualifier Rhyne Williams on Friday night. Williams ousted wild-card Marcos Baghdatis of Cypress 6-7 (7), 6-4, 6-2.

Nishikori was trailing Teymuraz Gabashvili of Russia 4-2 when he decided to stop the match because of a left hip flexor injury.

Gabashvili advanced and will play No. 7 seed Marin Cilic of Croatia, who defeated American wild-card Ryan Harrison 6-3, 6-4.

Copyright 2014 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

SI Apps
We've Got Apps Too
Get expert analysis, unrivaled access, and the award-winning storytelling only SI can provide - from Peter King, Tom Verducci, Lee Jenkins, Seth Davis, and more - delivered straight to you, along with up-to-the-minute news and live scores.