Usman Khawaja has led Queensland to the second biggest run-chase in Sheffield Shield history for a stunning comeback victory over South Australia.

Usman Khawaja showed how much he has left to offer as a Test batsman after leading Queensland to the second biggest run-chase in Sheffield Shield history on Saturday.

Dumped as Australia’s No.3 following their Ashes defeat in England last year, Khawaja batted for almost eight hours to guide the Bulls to a stunning comeback victory over South Australia at the Gabba.

Set 471 for victory, the Bulls charged to the target with five wickets and eight overs to spare as the Pakistan-born left-hander showed his class with a superb 182 not out.

It capped an amazing comeback as the Shield-leading Redbacks failed to enforce the follow-on after bowling Queensland out for 135 for a 268-run first-innings lead on day two.

Bulls skipper James Hopes said his players felt as though their season may have been over at the time, but they gained a new lease on life when the visitors declared at 6-202 in their second dig.

Hopes rated it an overly generous target for his fourth-placed side, that was always going to attack whatever big target they were set to stay alive in the competition.

“You never look a gift horse in the mouth, but it was a gift horse, that declaration,” Hopes told AAP.

“We were surprised we thought they would go a bit longer.

“We thought they would have batted us out of the game but they gave us a sniff and we took it.”

It was easily the Bulls biggest successful run-chase and only ranks behind South Australia’s 6-506 against Queensland in 1990-91 as the largest ever in Australian domestic cricket.

Resuming at 2-170, the Bulls lost only three wickets on the final day as the disciplined South Australian attack gained little help from the wicket before tiring late as Khawaja, Hopes (58) and Chris Hartley (48 not out) lashed them to all parts of the ground.

Khawaja and Peter Forrest laid the groundwork by putting together just 45 runs for the first session but the tempo of the innings built through the day in a well-measured approach.

Hopes hailed the effort of Khawaja, who he believes still should be rated among the best batsmen in the country despite being leapfrogged by Shaun Marsh and Alex Doolan in the Test team.

“Today he showed why,” he said. “That was a class innings.

“That’s one of those innings you dream about in your career and he pulled it off today.”

The only concern for Queensland, who now sit eight points behind leaders SA and NSW (24) with three rounds left, was Khawaja nursing a tight hamstring.

“I’m not sure whether it’s a cramp or a strain yet,” he said. “I was cramping up a lot after tea so hopefully it’s nothing serious.”