The teenage star won 3-6 6-3 7-6 6-3 and next plays Ukraine’s 13th seed Alexandr Dolgopolov for a likely fourth-round showdown with Roger Federer.
Querrey, 24, stands an imposing 198cm and serves with a venom to match his physique. He made full use of that weapon and his powerful forehand in the opening set in a packed Rod Laver Arena on Wednesday night.
Querrey gave up just four points on serve for the set, closing it out with two aces. He needed just one break, handed to him in fortunate style when Tomic fell over mid-point, the only time for the set he was down a break point.
But the 19-year-old showed typical composure to mix up his pace and shot style and work his bigger opponent around the court, as well as varying his position on return.
The tactics worked well, as Querrey gradually lost his early rhythm. A Querrey double-fault gave Tomic the pivotal break of serve in the sixth game.
But serving out the set was a huge struggle, Tomic needing six set points to clinch it, with Querrey producing some dazzling shots to deny the Australian on some earlier opportunities.
While former top 20 player Querrey, whose ranking has slumped to its current No 95 after an injury-hampered 2011, had the experience edge, it was Tomic who showed far more composure and poise as he raced through the pivotal third-set tiebreak.
From that point, he always looked the likely winner and he took the fourth set in less than half an hour, serving it out to love.
Tomic said it was a relief not to have been forced into another five-setter, after his tough Monday clash with Verdasco.
He said he was pleased with the way he had recovered after that match and with the way he weathered the early storm against Querrey.
“I did a good job to counter-punch in the second set and win it,” Tomic said.
He said his clash with Dolgopolov would be a huge challenge.
“Me an Alex always have tough matches,” he said. “He’s a very good player and I’ll have to play well to win.”