The 30-year-old has been restricted to six games this season after battling with an ankle injury.
But McDonald, who missed Melbourne's straight-sets exit from the finals last year, has got himself fit for Thursday night's clash with the Magpies in front of more than 90,000 fans at the MCG.
"He's got his timing right, Tommy, hasn't he," Demons coach Simon Goodwin said on Wednesday.
"He's played the last three games really well at VFL; now he's kicking goals, he's moving better, he's got his body 100 per cent fit and healthy.
"He's a really important player for us. He's a leader and he's proven that he can play well in finals footy."
McDonald booted 33 goals during Melbourne's 2021 premiership campaign, combining well with lethal left-footer Bayley Fristch.
The Demons will be without Jake Melksham, who performed admirably in the back-half of this season before rupturing his ACL in the final round clash with Sydney.
That win at the SCG was Fritsch's first appearance in two months due to being sidelined with a foot injury.
Fritsch starred with five goals in his return against the Swans but did send a scare through the Melbourne camp when he hobbled off with a sore foot.
"He's trained fully the last week so he's ready to go," Goodwin said.
"He did a fairly big running session on Saturday ... there's no questions about Bayley, he's a class player."
Up to 29 players took part in Melbourne's training run at Gosch's Paddock in front of a large contingent of Demons supporters.
Wet and cold weather is expected for the 1 v 4 battle, but Collingwood have already declared they intend to play both of their ruckmen, Darcy Cameron and Mason Cox.
Melbourne will almost certainly go with captain Max Gawn as their sole ruckman and again leave Brodie Grundy on the sidelines.
Grundy trained with the main group on Wednesday, but so did fringe players like Adam Tomlinson and Josh Schache.
