Tommy Paul defeated 24th seed Roberto Bautista Agut on Monday to reach his first Grand Slam quarter-final and set up an all-American clash at the Australian Open.
The world number 35 outclassed an opponent ranked 10 places higher 6-2, 4-6, 6-2, 7-5 on Margaret Court Arena in 3hrs 19mins.
He will face fellow unseeded American Ben Shelton for a place in the semi-finals after he beat another American, JJ Wolf, 6-7 (5/7), 6-2, 6-7 (4/7), 7-6 (7/4), 6-2.
With Sebastian Korda also through, the United States has the most men in the Melbourne Park final eight since 2000 when Andre Agassi, Pete Sampras and Chris Woodruff all got that far.
"That was a really physical tough match," said Paul, who has one career title, on hard courts in Stockholm in 2021.
"Any time you play Bautista it's going to be a war. I prepared for that match and I thought I executed it really well.
"I felt like I was running a lot though... so that wasn't a lot of fun, but happy to get through that one."