McCall played a 3-4-3 formation and saw his team run out comfortable winners thanks to a Jamie Murphy double and strikes from Tom Hateley and Michael Higdon.
Murphy was a missed penalty away from claiming a Clydesdale Bank Premier League hat-trick but Henrik Ojamaa was outstanding and ran the Dons defence ragged.
Motherwell had struggled to break down the Dons when losing 2-1 in a William Hill Scottish Cup replay earlier this month and McCall changed his formation to great effect as the Steelmen stretched their unbeaten SPL record against their opponents to 12 games.
McCall said: "I decided to match them and play three forwards up against their three centre-backs and I think with Murphy's two goals, one for Higgy and Henrik's performance too, it worked.
"It can be a dangerous game, but you have to have faith in your defenders and that your frontmen can do more damage to them than they can to you.
"I expected them to come and play the system they used in the Scottish Cup and for all the play we had we didn't cause enough problems but we can talk about tactics and formations all day.
"It's about players and if they go out and play as they can, they can trust us to make the changes. A few of the performances were outstanding."