"I don't think it was anything that didn't work for Sam. It was more Marin locking in and getting a good read on Sam's serve," Boynton said. "I haven't seen someone return Sam's serve like that in a long time."
Count him in: Sam Querrey looks toward next year's Wimbledon →
Boynton said Isner's neck began to stiffen after the Mahut match.
Marathon man Isner loses in 2nd round at Wimbledon →