It'll be Smith's Ashes if Australia prevail: Border

Former test skipper Allan Border says that if Australia take the last eight English wickets on the final day of the fourth Ashes test on Sunday and retain the coveted urn, the credit can go only to one man -- Steve Smith.

Smith has returned from his one-year ban for the Newlands ball-tampering scandal in quite sensational form and hit his ninth consecutive Ashes half-century with a knock of 82 on Saturday.

That took his tally to 671 runs at an average of 134 over the series, a haul all the more remarkable given he missed the third test after being struck on the head by a Jofra Archer bouncer.

It will be down to Australia's bowlers to ensure England, who will resume on 18-2 needing another 365 to win, do not produce another miracle recovery on Sunday to go with the one Ben Stokes conjured up in the third test at Headingley.

But even if Pat Cummins and co do achieve their task, Border thinks the entire team will need to doff their baggy Green Caps to former captain Smith.

"He's been quite phenomenal and if Australia go on to win this game and retain the Ashes, it's basically been on the back of Smith's bat," Border told Fox Sports TV.

"He's been phenomenal throughout the series and again yesterday, Australia in trouble as usual, top of the order struggling again.

"He just steadies the ship, and then that remarkable knock and gets them into position to declare and take those two late wickets which puts Australia right in the box seat going into day five."

While Smith has thrived in a series pushed back into the autumn to accommodate the World Cup, his fellow top order batsmen, with the exception of Marnus Labuschagne, have endured a torrid time in the face of the hostile English bowling.

"He's just a different class, it's as simple as that, he looks like he's playing in different conditions," Border added.

"The bowling looks less threatening when he's at the crease. All the other batsmen have really struggled.

"There's been some good bowling and the pitches have helped the bowlers a fair bit throughout the series ... but when Steve Smith's facing up, it's a different ballgame.

"He's just been the difference between the two teams to date."

If England manage to force a draw at Old Trafford, the series, currently tied at 1-1, will go down to the final test with Australian just needing to avoid defeat at The Oval to retain the Ashes.

Border, who scored 3,548 runs from 47 tests against England at an average of 56.31, was confident Australia would wrap it up in Manchester but felt changes would be needed if they fell short.

"I think we hold all the aces but if it's draw, they will have to look at that top order," Border said.

"They're just missing straight balls and they can't keep relying on Steve Smith to get them out of trouble, he's going to miss out eventually."