Australian Open: Dominic Thiem knocked out by world number 97 Tennys Sandgren

Tennys Sandgren is making his Australian Open debut

World number 97 Tennys Sandgren stunned fifth seed Dominic Thiem in five sets to reach the Australian Open quarter-final.

The American won 6-2 4-6 7-6 (7-4) 6-7 (7-9) 6-3 in three hours 55 minutes.

Sandgren, 26, had never won a match at a Grand Slam before this event and is only the second man in the last 20 years to reach a quarter-final on his Melbourne debut.

"I don't know if this is a dream or not," Sandgren said.

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The win was his second against a top-10 player in the competition after he beat three-time Grand Slam champion Stan Wawrinka in round two.

"Maybe guys aren't sure what to expect and don't know how I go about playing points," Sandgren said.

"I am using that to my advantage and I am just trying to ride the wave."

Sandgren had a match point in the fourth set tie-break which Thiem saved before going on to level the match.

But he broke serve in the sixth game of the decider before nervelessly serving out the match three games later, hitting his 63rd winner on match point.

He will play Novak Djokovic or Hyeon Chung in the last eight.