SYDNEY — Australia captain Steve Smith brushed off concerns about his fitness on the eve of the fifth and final Ashes Test against England on Wednesday before Mitchell Starc's return to spearhead the pace attack was confirmed as the only change to his team.

Left-arm quick Starc, the leading wicket-taker in the series after claiming 19 in the first three tests as Australia wrested back the Ashes, missed the drawn fourth test in Melbourne with a bruised heel but confirmed his fitness in the nets.

"Starcy's pulled up pretty well this morning and said he's ready to go," Smith told reporters at the Sydney Cricket Ground (SCG). "The break that he's had from bowling has helped his heel heal, it's coming on nicely, he's confident. You've got to take the player's words sometimes, and hopefully he gets through fine ..."

The Australia skipper, who has accumulated a series-leading 604 runs at an average of 151, left no one in any doubt that he would be leading his side out on Thursday despite missing training on Tuesday because of a bad back.

"It's a little bit stiff but nothing I haven't dealt with before," Smith said. "I'll have a good hit and a good catch today and I'll be fine tomorrow. I love batting out here at the SCG, it's my home ground and I've made a few good scores. So hopefully I can continue the run."

The side was confirmed after Australia's training session with Starc returning in place of Jackson Bird, who labored as a stand-in on an Melbourne Cricket Ground pitch rated as "poor" by the governing International Cricket Council.

Left-arm tweaker Ashton Agar was also brought into the squad to offer Australia the option of going with two spinners if it looked like the SCG was going to offer a lot of turn.

Smith, though, said the state of the pitch made it unlikely that one of the quicks would make way for Agar to play alongside off spinner Nathan Lyon as the hosts look to wrap up the series 4-0.

"The wicket's got a fair bit of grass and looks to be a pretty good wicket," he added. "I'd say we'd probably opt for just the one spinner."

Meanwhile, Mason Crane's introduction to Test cricket for the fifth and final Ashes clash with Australia is perhaps a sign that England are finally prepared to invest the time it takes to develop a decent leg-spinner, whatever the short-term cost.

At 20, Crane will be the youngest England spinner for 90 years to make a Test debut when he wins his first cap at the Sydney cricket Ground on Thursday in a series that England trail by an irretrievable 3-0.

In the corresponding fixture on the 2013-14 Ashes series, when England were 4-0 down, Scott Borthwick, Boyd Rankin and Gary Ballance were all handed debuts with only the latter going on to play a second Test.

Crane's elevation after taking 75 wickets at 44 in 29 first class matches could be seen in the same vein but for Joe Root's assertion to the contrary as he plots a win that he thinks is vital to England's success on their next trip Down Under.

"I want us to be the best side in the world ... and it's not going to happen by chucking guys in for the last game of a series," he said.

"So it’s really important that we do it in a way which, over the next four years, gets us in the best place to perform well here, but throughout that period being as successful as we can be."

The art of spinning the ball away from a right-handed batsman using the fingers and a full flick of the wrist can produce spectacular results but also be difficult to control.

Borthwick's return of 4-82 from his leg spin in a losing cause at the SCG in 2014 was decent enough but he never played another test, while Adil Rashid has since ended up on the Test scrapheap after 10 matches, all abroad.

Crane's development may mark a sea change to this attitude and, while still not a regular for his county Hampshire, he has already played two T20 internationals.

He linked up with MacGill when he came over to Australia in 2016-17 to play for Sydney's Gordon club and three seven-wicket hauls earned him a New South Wales call-up, the first for a foreigner since Imran Khan in 1984-85.

He took 5-116 in his only Sheffield Shield game against South Australia, a match played at the SCG where he will make his debut on Thursday after once again working with MacGill. — Reuters