The first-choice opening batsman missed the first two Tests due to a groin strain.
Warner has been under rehab for a groin strain he picked up while fielding in the second ODI against India at the start of the summer. An explosive batsman, who could set the mood of the innings with his strokeplay at the top, Warner is expected to rejuvenate the struggling home team batting unit with his presence.
"That's a real, clear option. He may not be 100 per cent fit — who is coming off an injury? You never know until you get out there," McDonald said during a virtual press conference, as quoted by PTI.
"Look, if he's 90-95% fit and the conversation is that he's fit enough to be able to go out there and perform his duties for the team, then I'm sure that'll be a conversation the coach has with the player."
"Most times Justin (Langer) is pretty open with the players in terms of giving them accountability around that."
Signalling he is on track to regain fitness, Australia on Wednesday (December 30) reincluded Warner in the Test squad. The hosts are hoping to get back to winning ways after being dominated by the Indians across four days in the Boxing Day Test at MCG.
"He's (Warner) very optimistic that he should be ready to go, which is a great news for us. We are really excited to have him back," McDonald said.
"I'm sure that he's excited to come back into the group as well. There's nothing worse than being injured when you are at the top of your game as David has been over a period of time."
Australia have also excluded out-of-form Joe Burns and brought back Will Pucovski, raising the possibility of Pucovski's Test debut after overcoming a concussion scare. The right-hand batsman from Victoria was primed to play in the first Test itself but had to be sidelined following a blow to his head while batting for Australia 'A' in a pre-series warm-up game.
"He will be put through tests whatever it needs to be put through to make himself available for selection to potentially open the batting. So it's good to have a little bit of depth out there," said McDonald.
McDonald refused to read much into the failures of Steve Smith in the Test series so far. The great batsman has managed just 10 runs from his four innings in Adelaide and Melbourne.
"I wouldn't be too quick to be judging Steve Smith not looking good in the middle. He looks pretty solid and hitting the ball well at the nets," said the former Aussie cricketer, who also declined suggestions that an extended period within bio-bubbles has taken a lot of mental toll on Smith.
"No, none whatsoever. Obviously we worked closely at UAE with the Rajasthan Royals and there's nothing to suggest that there's a link there."
"I'm sure ideally you would prefer to be with your family around Christmas time and Justin addressed that. Some players and staff members unfortunately are going to be disconnected from family during Christmas time, less than ideal there's no doubt," he said.
"Yeah, it's a challenge to rebound. The world's best players usually rebound. He's (Smith) in a really good space to be honest, come Sydney Test."
McDonald held the same belief for Marnus Labuschagne, another of Australia's key batsmen.
"Technically they're ready to go," he said. "It's about how they score their runs and how they're going to combat these attacks from Indian bowlers. Yes, they want to make sure that they are technically in a good space but it's more about the method now."
"Probably the question for me at the moment is the technical or technically the way that India have prepared and able to probably control particularly with that sort of leg side theory, so to speak."
India's planning to both Smith and Labuschagne has been top-notch this series, especially when it comes to the use of premier off-spinner Ravichandran Ashwin. After scoring just 191 in the first innings in Adelaide, the Australians managed totals of only 195 and 200 in Melbourne.
McDonald said they were surprised by the bounce and turn which the surface at MCG had.
"I think one of the things that really surprised everyone was the surface at the MCG on Boxing Day. It hasn't been what we've normally assumed to be flat strength," he said.
"We weren't expecting the spin to play a significant role at MCG on day one in particular. It spun and bounced off the main part of the surface. So, to me the wicket probably surprised us a little bit."
"We probably weren't able to adapt quick enough during that period of time to combat Indian bowlers," McDonald added.