MacGill battled knee problems in Australia's 96-run victory over Sri Lanka in the second Test here this week and has to work on his physical shape, new coach Tim Nielsen said.
The 36-year-old wrist-spinner, who finally got his chance to claim a regular Test place with the retirement of champion leg-spinner Shane Warne, laboured against the Sri Lankans, taking 2-81 and 1-102, and had difficulty with his flight and length.
Skipper Ricky Ponting showed his faith in MacGill by giving the leg-spinner four overs on Tuesday's final day after his pounding by the Sri Lankan batsmen on Monday.
He returned 1-9 before the second new ball was taken and Australia wrapped up a convincing win.
But MacGill clearly has fitness issues which coach Nielsen wants to address.
"We do play back-to-back Test matches all through this summer, we've got two blocks of Test matches (against India) over two weekends," Nielsen said Wednesday.
"If you can't physically cope, and it's just not Stuart MacGill, there is no way you can give yourself the best chance of executing your skills to the level you need to be successful.
"Stuey has some work to do, we have Andrew Symonds who has an injury issue at the moment.
"Stuey came off surgery six weeks ago so he's really working hard to get that right and we're encouraging him to get as fit as he possibly can and maintain his work on his skills.
"It's nice now to have a break and freshen him up and get as fit as we can for Melbourne."
Ponting said MacGill has a few weeks to get things right.
"He only plays one form of the game these days so I'm not sure how much cricket he's going to get under his belt or if he's better off just trying to have a few weeks off and get his body right," Ponting said.
"There is an opportunity for all of us. I think we've got a couple of weeks before the Chappell-Hadlee one-day series (against New Zealand) starts and probably a month before the India Test match comes around so there will be an opportunity for all of us to play some state (Sheffield Shield) cricket."
MacGill has an outstanding Test record with 203 wickets in 42 Tests.
Nielsen said Symonds has been cleared of serious ankle injury and would begin rehabilitation work after sitting on the sidelines for most of the Hobart Test.