The former Rangers, West Brom and Dundee United midfielder was confirmed on Monday as successor to Craig Brown who is to join the Dons board at the end of the season.
However, the 72-year-old former Scotland manager will take charge for Aberdeen's last two matches before the split, against the Jambos and Dundee United as the Granite City side, currently ninth in the table, try to achieve a top-six finish.
MacDonald, 26, expects the Dons players to be fired up further, knowing that McInnes is watching.
"After Craig Brown announced that he was going to step down, why not get a new manager in and let him get his ideas across and build for next year," he said.
"I'm sure the new manager will bring in his new ways so it is probably good for the club overall, instead of waiting for the summer, it will give them a head start for next season.
"The players will be thinking of the new manager coming in and will be wanting to impress him.
"It is pretty much a clean slate for everybody so it will obviously be a bit of a lift for the players."