Panesar will be assessed on Thursday, but it is believed England are set to call up 23-year-old Durham legspinner Borthwick as they look to avoid a 5-0 whitewash and look to the future.
It is not the first time England have looked to blood a young slow bowler in a dead-rubber Ashes Test, after Simon Kerrigan made his debut in the fifth Test at The Oval in August.
The match ended in a draw but Kerrigan was slaughtered by the Australian batsman - going for 53 runs from his only 48 balls in Test cricket.
Kerrigan hasn't been seen since, with Borthwick instead called into the England squad following the retirement of Graeme Swann before the Melbourne Test.
Borthwick had a stint with Sydney first-grade side Northern Districts and was about to fly home when the call came.
Australian vice-captain Brad Haddin played alongside him for Northern Districts earlier in the summer, but said Borthwick could expect a stern test of his mettle.
"No doubt (we'll get after him)," Haddin said.
"It'd be an exciting time for him. But interesting to see how we approach him."
Australia belted Swann in the first three Tests and Panesar was largely ignored in the Melbourne match - with captain Alastair Cook opting to bowl part-timer Joe Root ahead of him during Australia's second innings.
But Borthwick said he welcomed the challenge set down by Australia.
"If they do, I'll accept that challenge," said Borthwick, who regards Shane Warne as his inspiration.
"I'll try and spin the ball and give it my best shot.
"It's been an amazing two weeks. I'm thrilled. I didn't think I'd be here. But I am now."