Sam Querrey edged past his doubles partner and Davis Cup team-mate John Isner in three sets to win the ATP Regions Morgan Keegan Championships in Memphis on Sunday.
Querrey, the eighth seed who defeated defending champion Andy Roddick in the second round, fought back from a set down to defeat fellow American Isner, the sixth seed, 6-7 (3-7) 7-6 (7-5) 6-3.
The 6ft 9in Isner was two points from victory at 5-2 up in the second-set tie-breaker but his 6ft 6in opponent rallied to secure the third ATP Tour title of his career.
"At 5-4 and 5-5 in the tie-break he missed serves by an inch," Querrey said. "I got lucky there."
Isner acknowledged Querrey had held his nerve when it mattered, saying: "I had the match on my racquet. 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."
"I didn't do enough with the 5-5 volley and it cost me."
Querrey, who served up 17 of the match's 36 aces, was thrilled to clinch the title but admitted it had been difficult playing against his close friend.
"It feels great," said the 22-year-old. "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."
"This is the first time we played. Hopefully in the next 10 years we'll play another 10 or 15 times."
"He'll win some of those and I'll win some of those - it's tough, but something we'll deal with."
Meanwhile Australia's Jordan Kerr and Great Britain's Ross Hutchins were beaten in straight sets in the doubles final.
Davis Cup duo Isner and Querrey triumphed 6-4 6-4 with the minimum fuss to claim the title.