MacGill has been suffering from knee and hand problems and struggled to produce anything like his best form during Australia's 2-0 win over Sri Lanka.
He took just five wickets in the series at an average of 65.20 and was completely out of sorts in the second innings of the second Test in Hobart, bowling a string of full tosses and long-hops.
Australia coach Tim Nielsen said MacGill deserved another chance but needed to get back to peak fitness before India arrive next month for four Tests in a 34-day period.
"I think he realises that he has got some work to do physically to get himself up to a level which is going to allow him to play back to back Test matches and fulfil the role that we need him to do which is to bowl big blocks of overs one end to allow our quicks to keep churning away from the other end," Nielsen told a news conference in Hobart.
"We play back-to-back Test matches all through this summer and if you can't physically cope...there is no way they can give themselves the best chance of executing their skills to the level they need to be successful.
"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."
Captain Ricky Ponting said he regarded MacGill as Australia's best spinner since the retirement of Shane Warne but admitted were concerns about his fitness before the first Test starts in Melbourne on Dec. 26.
"There is no doubt he has carried a few things through this game with his finger and his knee giving him a few troubles," Ponting said.
"He has got a few weeks to get his body in the best shape he possibly can.
"If he gets his body right and he's fit then I think he will probably be the number-one choice spinner."
Australia had few problems completing a series whitewash over Sri Lanka but expect India to present a bigger challenge.
"I think coming to Australia excites them, they like playing against us and they'll usually - in Melbourne and Sydney especially - have good support for them there," Nielsen said.
"Melbourne's always a massive Test as well, so to come into that environment and just be part of it all will just get them going."