Tennessee-born, tennis-loving Tennys Sandgren has caused one of the biggest upsets at the Australian Open knocking out fifth-seeded Dominic Thiem to advance to the quarter-finals.

Previously winless at grand slams, the aptly-named American continued his astonishing run at Melbourne Park with a 6-2 4-6 7-6 (7-4) 6-7 (7-9) 6-3 victory in three hours and 54 minutes.

His reward will be a final-eight showdown with either six-time champion Novak Djokovic or South Korean rising star Hyeon Chung.

“I don’t know if this is a dream or not,” Sandgren said.

“All of you guys are here and I’m not in my underwear, so maybe it’s not a dream.

“This is my fifth Australian Open; I’ve lost in (qualifiers) four years.

“This is my first main draw at the Australian Open and now I’m in the quarter-finals.”

Sandgren arrived at Melbourne Park having only twice made the main draw of a major from 15 attempts.

The world No.97 scored a US Tennis Association wildcard entry to last year’s French Open.

He was then bumped up to the main draw of the US Open when Japan’s Yoshihito Nishioka withdrew through injury.

Both times, he was beaten in the first round.

Sandgren has now seen off two of the top men’s seeds, having defeated an injury-hampered Stan Wawrinka in the second round.

He is just the second man in 20 years to make the quarter-finals of the Australian Open in his first main-draw appearance.

“He’s a heck of a player, so I knew I had to come out and play aggressive and take my chances and serve well,” Sandgren said of Thiem.

“Thankfully, it worked out in the end.”