"It's tough playing your good buddy like that -- if anyone else could win the tournament, I'd want it to be him, so you're not going to get the same reaction from me about it than if I were playing someone else," Querrey told reporters.
"He'll win some of these and I'll win some of these."
In a battle of big serves from big men, Querrey is 6-foot-6 and Isner 6-foot-9, neither player was able to break the other in the first two sets.
"I had the match on my racquet," Isner said.
"He played well when it counted though, better than me. It's really hard, because I like to think I've played really well in those situations in the past."
(Reporting by Jahmal Corner in Los Angeles; Editing by Peter Rutherford and Ian Ransom)