Unheralded Jordan Thompson stunned world number 15 Jack Sock in four sets in the opening rubber of the Davis Cup quarter-final between Australia and the USA in Brisbane on Friday.
Thompson, ranked 79th in the world, held his nerve to see off a faltering Sock 6-3, 3-6, 7-6 (7/4), 6-4 in front of a raucous crowd on Pat Rafter Arena at the Queensland Tennis Centre.
With in form Nick Kyrgios still to play on the opening day, Thompson's shock result gives Australia a good chance of reaching just their second Davis Cup semi-final since 2006.
"It's huge to play for your country -- another shot at a five set match, playing quality opponents, it's big," Thompson said.
"It's great to take your game to the next step."
Thompson, playing only his second Davis Cup tie, went into the match against the American number one as the huge underdog.
He struggled to stay with Sock in the opening set but seized his chance when the American's serve deserted him at 3-4, breaking Sock to win the opener in 37 minutes.
Sock found his range with his booming forehand and stormed back to take the second.
The American number one looked the more dangerous in the third but Thompson held on to force a tiebreak, gaining a vital break before taking the set when Sock double-faulted.
Thompson carried all the momentum with him into the fourth set against an increasingly tired looking Sock and closed out the match in three hours.
"He played a good match -- he deserved to win," a disappointed Sock said.
"He served well, made a lot of balls."