next Image 1 of 2

prev Image 2 of 2

The last American man standing at the Australian Open is through to the quarterfinals.

Tennys Sandgren, who had never won a Grand Slam match or beaten a top 10 player before the tournament started, upset No. 5-seeded Dominic Thiem on Monday to top his second-round victory over 2014 champion Stan Wawrinka.

The 26-year-old Sandgren, who entered the season's opening major ranked 97th, missed a match point in the fourth set but held on for a 6-2, 4-6, 7-6 (4), 6-7 (7), 6-3 win over Thiem.

"I'm staying calm and not getting too upset, not getting too up, not getting too down," Sandgren said when asked how a player with only two ATP tour match victories kept believing he had what it takes to advance to a Grand Slam quarterfinal.

"I've been able to keep my emotions under control, which is a big deal because I can be an emotional person. That doesn't go well with tennis, especially with a three-out-of-five-set match. You don't have energy to waste on emotions."

He is only the second man in the last 20 years to reach the quarterfinals in his Australian Open debut — Alexandr Dolgopolov did it in 2011. Before that it was Nicolas Escude in 1998.

Most of his Sandgren's other Grand Slam appearances have been forgettable — first-round losses as a wild-card entry at last year's French Open and U.S. Open. The Tennessean failed to qualify for a major in 13 attempts, including from 2013 to 2016 at Melbourne Park.

Even his build-up for Melbourne was brief: first-round losses in India and at Auckland, New Zealand.

So while seeded U.S. men such as No. 8 Jack Sock, No. 13 Sam Querrey and No. 16 John Isner all went out in earlier rounds, Sandgren is through to the final eight.

After his match, he was asked at a news conference about the nature of some of his social media tweets, suggesting he follows some accounts or retweets items from controversial right-wing sources.

"Look, who you follow on Twitter I feel doesn't matter even a little bit," Sandgren said. "I think it's crazy to assume that. To say, 'Well, he's following X person, so he believes all the things that this person believes.' I think it's ridiculous."

He was asked if he supports any far-right movements.

"No, I don't. I don't," Sandgren said. "I find some of the content interesting. But no, I don't, not at all. As a firm Christian, I don't support things like that, no."

In the quarterfinals on Wednesday he'll play Hyeon Chung, who upset six-time Australian Open champion Novak Djokovic in straight sets.

Sandgren lost to Chung in Auckland two weeks ago, and he credited his form in that loss — 6-3, 5-7, 6-3 — with forcing improvements in his game.

"I feel like we had a tight contest," Sandgren said. "I feel like I had to raise my game to even compete with him on the court. I think that helped me a lot going into this week, seeing I could play a good level. That made me feel like, 'OK, maybe I can do it in three-out-of-five sets, on a bigger stage, against other players, too."

Thiem was full of praise for Sandgren.

"I didn't play bad, it was one of these days where you have to give a lot of respect to your opponent," Thiem said.

"He served very well. I had lots of problems to return his serve. Then he didn't make too many unforced errors, it was very tough for me to finish the points. He didn't really drop for almost four hours."

For the time being, Sandgren is living the dream. Seriously.

"Obviously the first three matches were more than I expected," Sandgren said. "This one was about as hard-fought as I've ever had a match before. I definitely had a real pinch-me moment. If I wake up now, I'm going to be real upset."