Delray Beach: US second seed John Isner rallied Friday to reach the ATP Delray Beach Open semi-finals, where he will try to deny Marin Cilic his third final in as many weeks.

Big-serving Isner fired 18 aces in outlasting US qualifier Rhyne Williams 4-6, 6-3, 6-2 while Cilic, a seventh seed from Croatia, dispatched Russia's Teymuraz Gabashvili 6-2, 6-3.