Friday's second singles match pitted two of tennis' most dominant servers, the 16th-ranked Kyrgios and 23rd-ranked American John Isner. Sam Querrey and Steve Johnson - known as "Quonson" to US team captain Jim Courier and others - would have to lead the way to an unlikely win on doubles-only Saturday because the U.S.is down 2-0 in the best-of-five competition.
Hewitt said it was no surprise Sock - the highest-ranked player in the tie - was subbed into the doubles after United States captain Jim Courier had telegraphed the possibility of a late change.
Former Australian tennis player Todd Woodbridge says that Nick Kyrgios' game has a taken a positive step forward. The controversial Australian pushed Roger Federer to the brink in Miami last week and he carried that form into Friday's match.
Following the win, Kyrgios said: "That was a lot of fun". I still throw my racquet and still swear, but I will compete for every point.
"I still am very emotional out there".
"I just tried to wear him down, and I thought I was fit enough to do that", Thompson said.
Hewitt did not rule out making a change to his doubles line-up with John Peers and Sam Groth scheduled to meet Sam Querrey and Steve Johnson for the third rubber, but teams can make changes on Saturday morning under Cup rules.
"The way Thommo went out there and backed himself under pressure, that's how I dreamt of his match playing out", an elated Hewitt told the press. 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.
United States of America captain Jim Courier preferred Sock to Sam Querrey and his faith was repaid, with the duo coming back from a set down to take it to five and eventually see out the contest 3-6, 6-3, 6-2, 2-6, 6-3. Jordan set the standard earlier.
The Koreans suffered a setback before the tie started when two top players pulled out, leaving 19-year olds Kwon Soon Woo and Hong Seong-Chan to shoulder the burden.
He smirked at a suggestion a five-setter would hand an advantage to Isner.
Focus will now shift to reverse singles where Nick Kyrgios is slated to face Sock in Sunday's first rubber. The victor of the tie will remain in Asia/Oceania Group 1, while the loser faces a play-off later in the year to avoid relegation to group 2.
Thompson's previous best win also came at Rafter Arena, when he beat world No.21 David Ferrer on the way to his first ATP quarter-final in Brisbane in January.
Kyrgios had some great outings during his recent great stretch, defeating world number two Novak Djokovic in straight-sets at Acapulco and Indian Wells.
"You've got four players in the team for a reason".
The victor of the quarter-final will face either Belgium or Italy in September's semis.