Australia head coach and selector Andrew McDonald has confirmed Usman Khawaja will play in the fifth Ashes test against England at the Sydney Cricket Ground amid media speculation it could be his last international.

The oldest player in an ageing squad, the 39-year-old lefthander's spot in the line-up is under scrutiny following his demotion down the batting order and as selectors look to the future.

With the promoted Travis Head taking his opening spot, Khawaja batted at number four in the third Adelaide test and number five in the fourth match in Melbourne.

While some reports in Australian media have suggested Sydney could be Khawaja's last international, McDonald said he had not had any conversations with him about his future.

"There's no indication at my end that he's calling it in Sydney," McDonald told reporters in Melbourne on Monday.

"But his performance in this calendar year has been good enough to warrant selection so I'd say he'll be there marking centre in Sydney."

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Khawaja has not spoken publicly of his plans and returned home to Queensland for a break with family ahead of the Sydney test, which starts on January 4.

The 87-test veteran suffered back spasms during the first Ashes test in Perth and missed the second match in Brisbane.

He is averaging just over 30 with the bat in his three Ashes tests and scored 82 at Adelaide Oval to help Australia seal the series with two matches to spare.

However, he scored 29 and zero in his two innings in the fourth test in Melbourne as the hosts slumped to a four-wicket defeat.

While criticised for a soft dismissal in his second innings in Melbourne, Khawaja's numbers stack up better than several Australian batters this series, including opener Jake Weatherald, Marnus Labuschagne and all-rounder Cameron Green.

On the bowling front, Australia will again be without three of their world-class bowlers in Pat Cummins, Josh Hazlewood and Nathan Lyon in Sydney.

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Cricket Australia (CA) said in an injury update on Monday that Lyon would not play any further part in the home summer after having surgery on a high-grade hamstring injury he sustained during the third Ashes test.

A target date for his return would be determined later.

CA said Hazlewood had started running again after hamstring and Achilles injuries and was on track to play in the T20 World Cup starting on February 7.

McDonald said Cummins would be included in Australia's squad of 15 for the World Cup, to be co-hosted by India and Sri Lanka, but would need to be cleared by a scan on his lower back.

"Pat will have a scan, I think in another four weeks, so that'll give us the information then on where he's at for the World Cup," McDonald added.