McGrath, who needed a painkilling injection to see out the first Test, will have to be certain he can get through five days of cricket to start the match on Friday, Ponting said on Thursday.
"I won't know more on him until tomorrow morning. Our physio wanted him to have a good long bowl today and see how he pulled up in the morning so it will be tomorrow morning until we know about him," Ponting told reporters.
The 36-year-old paceman, who took seven wickets as Australia won by 277 runs at the Gabba, appeared tentative in his first overs in the practice nets Thursday.
He later spent time with team physiotherapist Alex Kountouris discussing his troublesome callous on his left heel.
"That is as good as I could have hoped," McGrath said.
"I'm really happy there. What we've done has worked.
"What I feel now is what I've felt in other Test matches that I've played and got through easily. If it's up to me I'm in. There's no problem."
Ponting said McGrath will have to be completely fit to take his place in a four-man bowling attack that needs every bowler pulling their weight on the even-paced Adelaide wicket.
"Glenn's got to be 100 percent going into the game, with our team balance likely to be the way it is we can't afford to be carrying any of our bowlers whatsoever," Ponting said.
"So Glenn will have to give me what I require of him through the course of the game, and if he can't then a few more questions will be asked."
But Ponting still hopes McGrath will play on Friday and said the old stager had visited a podiatrist to change the specially modified inner soles, or orthotics, in his shoes to take pressure off his heel.
"It is only a blister so they can't see why it is going to get any worse. It is something he has actually had for 15 years in his career and it just got a lot worse last week, and it was something that had to do with his new orthotic that made it happen," he said.
Although confident, McGrath told a radio station the pain was the worst he had experienced while bowling throughout his first-class career.
"It must be quite a sensitive area because when I was bowling the other day, I've bowled through some pain previously, but that's as bad as I've ever bowled through," he said.
"For something so minor, it (the pain) was ridiculous."
McGrath took 6-50 in the first innings of the Gabba Test and finished with seven match wickets as Australia won by 277 runs.
His situation has parallels with last year's Ashes series when he took nine wickets in Australia's rousing win in the opening match only to miss the second Test after injuring himself in the warm-up.
England won the second Test and went on to reclaim the Ashes series for the first time in 18 years.
Australia have won only 18 of the 33 Tests that McGrath has not been available, or a 54 percent success rate, compared to 67 percent winning ratio when he takes his place in the bowling line-up.
Australian selectors have placed pace bowlers Shaun Tait and Mitchell Johnson on standby as a replacement options should McGrath not be fit to play.