Former Australia paceman and Macquarie Cricket commentator Glenn McGrath warned selectors not to risk star quick Mitchell Starc for the final Ashes Test with a tour of South Africa looming.

Starc was a notable absentee for the Boxing Day Test in Melbourne due to a bruised heel as Australia and England played out a draw in the fourth match.

The leading wicket-taker in the Ashes with 19 to help Australia reclaim the urn, Starc was back in the nets on Tuesday and he showed no signs of discomfort.

However, McGrath would only play Starc in the Sydney Test if he was 100 per cent fit ahead of the South Africa tour, which gets underway on March 1.

“Someone who bowls at that pace, attacking lengths that he bowls and swings the ball.

“You want him playing every game possible, especially at his home ground here.

“But with a big tour of South Africa coming up … if he’s 100 per cent fit I’d play him.

“If he’s not quite there, unfortunately [they] might have to let him have a rest and have him ready for South Africa.”

Australia team-mate Pat Cummins, however, is confident Starc will return to the bowling attack at the SCG on Thursday.

“I haven’t spoken to him but it looked like he was bowling quick, running around and wasn’t limping,” Cummins said. “I know he’s really keen to play and he’s pretty confident he’s going to play.

“Now it’s seeing how it recovers. He said it’s got better the last week or two since Perth. So hopefully he gets through today and he’s alright.”