Four forced changes and one omission from last week's side gave the Collingwood coach the opening he needed to bathe another youngster in the finals cauldron.
Macaffer, 21, had played just three senior games before Saturday night, and had not been in the side since round seven.
"We know he has a lot of faith in us young guys," the former rookie said, when asked about the less-experienced players' relationship with Malthouse after the Magpies' thrilling five-point semi-final win over Adelaide.
"There's a lot of talented players back in the twos, and it's great that you can know there can be five changes and blokes can come in and get a role to play, and they'll do it."
The gamble on Macaffer's inclusion paid dividends. After a relatively quiet first half, he lifted when his side did and collected 12 possessions after the main break – 18 for the game.
He also made two timely contributions in the fourth term, with a goal at the 19-minute mark bringing the Pies within a point, and a behind a minute-and-a-half later levelling the scores.
"I pretty much just did not want to kick it out on the full," he said.
"I was very nervous running in, and then to see it go straight and through the middle was awesome."
Macaffer, who Malthouse said "ticked boxes under pressure" in the game, said simply being named in the side was a momentous occasion for him.
"There were a number of guys that could have come in, because we've got heaps of guys down at [VFL level] that have been playing outstanding, and I was lucky enough to get the nod," he said.
"I got to come in and play in this fantastic win.
With the availability of Scott Pendlebury (leg), Dayne Beams (calf), Josh Fraser (knee), and Anthony Rocca (ankle) unknown for Saturday night's preliminary final against Geelong, Macaffer doesn't know what his immediate future holds.
Against the Crows, Macaffer said Malthouse had focussed on a return to the game plan at half time.
"They got the better of us in the first half, but we were able to get back to our structures and our game plan, and wear them down in the end," he said.
"We came in at half time and we reinforced what we needed to do to get ourselves back in the game.
"We knew if we could stick to what we'd been doing, we'd get back, and it paid off."
He also said the leadership of Nick Maxwell, who played a brilliant captain's game for 22 touches and five tackles, had been invaluable to the Pies' success this year.
"He's a fantastic leader. You couldn't say a bad thing about him, with the way he goes about it on the field," he said.
"He gives direction and he runs back with the flight of the ball; he's just awesome.
"You couldn't ask for a better captain."
