Maxwell was riding on the buggy following playing a round of golf ahead of their contest against the defending champions in Ahmedabad on Saturday when he fell off the back.
Cricket Australia's concussion protocols mean that Maxwell's condition will be monitored for a few days.
"He's doing fine, he'll start some light exercises today and we feel as though it will be a reasonably straightforward return to play protocol," McDonald told reporters.
"I suppose the fortunate part was there was no other injury sustained which could have been a lot worse than it is. I think it rattled everyone to be fair once it came to the conclusion there was a concussion and he was going to miss a game.
"There was nothing untoward in the behaviour throughout the day, it was a clear-cut accident. Unfortunately, it's compromised what we are doing as a team."
Maxwell broke his leg in a freak accident at a birthday party in Melbourne last November and had also missed Australia's recent tour of South Africa with an ankle issue.
Maxwell has been in superb form in the tournament and hit a 40-ball hundred against the Netherlands.
"There's no doubt it leaves us a fraction exposed at the back end in terms of how Glenn's been performing," McDonald added. "But Marcus Stoinis does become available, all things going well at training today."
Australia will take on Afghanistan and Bangladesh after the game against England.
