The best Australia had to hope for achieving out of their practice match against Northamptonshire - once the rain that ruined day one finally lifted - was a quick and easy confidence booster in the aftermath of their Ashes defeat.

They got neither, as a former Australia under-19s peer of Shaun Marsh and George Bailey belted an unbeaten century to take his team to a commanding 396. That batsman, 32-year-old Steve Crook, struck 24 fours and four sixes in his 142 not out from 96 deliveries.

Australia's task of surviving the final five overs of the day unscathed proved too hard, with David Warner edging to first slip for six. They will resume the final day at 1-13, trailing by 383, with Shaun Marsh on 7 and Steve Smith due to be next in.

Mitch Marsh was the best of Australia's bowlers, claiming 4-56, with Nathan Lyon and Pat Cummins each finishing with three wickets.

Peter Siddle was miserly with the new ball, but only bowled one over with the second new ball before leaving the ground. His teammate Lyon said he thought the fast-bowler, an unused squad member for Australia's six Tests in the West Indies and England since the home summer, was fine. "I think he's OK," Lyon said.

Leg-spinner Fawad Ahmed's bad week, which began with chief selector Rod Marsh publicly downplaying the prospect of him holding his position in the squad for October's Tests in Bangladesh, got worse as he was pummeled for 48 runs in six overs.

Ahmed was not used until the 42nd over and only bowled three spells as he was hit for seven fours and a six.

Captain Smith chose to field first on winning the toss yet saw his team take only two wickets in the first 51 overs as hard-hitting opener Ben Duckett and Scotland international Kyle Coetzer, who played against Australia in the World Cup earlier this year, each made half-centuries.

When Coetzer fell for 86 the decision of Smith's to send them was on track to be justified. At that stage Crook, who grew up in Adelaide but has been based in England for the past 13 years, was on only 4. Within 20 overs he was, remarkably, on the cusp of a century.

Crook was given a life on 91 at cover by Shane Watson, off the bowling of Marsh.

At one stage he was a realistic chance to run out of partners when Ben Sanderson and Maurice Chambers fell within an over of each other, leaving Northamptonshire on 9-344 and him three short of his milestone.

Crook deservedly brought up his century, from just 77 deliveries, by pulling Marsh into a gap between deep square-leg and fine-leg. He then clubbed three more boundaries to take 18 from that over.

He struck consecutive sixes off Nathan Lyon soon after and was then starting to take to Shane Watson when his last partner, Richard Gleeson, became Cummins' third victim.

Crook's memorable day was capped by him taking the catch at first slip to remove Warner, off the bowling of Chambers.

"My under-19s year had Shaun Marsh, Shaun Tait, Mark Cosgrove, Cameron White, Xavier Doherty, George Bailey, so we had quite a good crop of players," said Crook, who left Australia in 2002 to play club cricket in England and stayed when he earned his first professional deal.

"It's interesting to see how those guys have developed and gone on to play all over the world. To be part of that generation of players is really cool."

Lyon, who joked it was worth checking if Crook still held an Australian passport, praised the 32-year-old for his innings,

"You've got to give credit where credit is due. Crook played an unbelievable innings," he said. "We probably didn't bowl our best, and in these games the batters tend to play with a lot more freedom and no fear, so they took they chances and he hit them pretty well."