The Hibernian player had scored 13 goals in 13 games going into this encounter; the Aberdeen man seven in eight.
As Griffiths launched a long-range barrage at visiting goalkeeper Jamie Langfield without finding a way through, McGinn waited for a clearer shot. When it came, 14 minutes from time, it was enough to take his team to within a point of the champions and ahead of Hibs on goal difference – this despite Aberdeen being reduced to a bench made up almost entirely of rookies.
First on the draw was Griffiths, cutting in from the left and twice feigning to shoot before unloading with his left foot. Aberdeen captain Russell Anderson took one for his team, right between the eyes. The defender wobbled, his arms swinging loosely by his sides, like Robocop under a hail of bullets, but he did not drop. Old school.
McGinn shot back. Johnny Hayes improvised a dinked pass over the Hibs defence and the forward, playing wide left for an Aberdeen team stripped to its bare bones, lined one up from the edge of the box. His shot started well outside the post and curled in, but not quite enough.
The Northern Irishman reloaded. Josh Magennis crossed from the Aberdeen right and it looked like an invitation for McGinn, but he got his jump wrong and came up a fraction in front of the ball with the result his header went up instead of in. As the first half wound down, Griffiths pulled the trigger twice in a minute, drawing two saves from Langfield.
First, the striker cut in from the left and, from the corner of the box, slashed through a left-foot shot that moved from left to right; Langfield sprang to his right to make the save. Then Griffiths broke a couple of challenges and hit a low drive the goalkeeper dropped on clumsily, saving with his torso more than his hands.
The second half began with Griffiths on target again, with his most audacious effort yet. A cross from the left by Lewis Stevenson found the striker back-tracking beyond the far post, but he spun into an overhead kick that needed a smart reaction save from Langfield, who was recovering his position after missing the cross.
Ten minutes later Griffiths was driving at Mark Reynolds after the two were isolated by a quick throw-in, turning him this way and that and then hitting a drive from the edge of the box that Langfield fielded low and to his left.
Next, he danced between Magennis and Anderson but rolled his shot across the Langfield and just wide of the far post. It was a rarity, a Griffiths shot that failed to hit the target. It looked like the duel was between Griffiths and Langfield.
It was not. Hayes crossed low from the left and Alan Maybury got his studs on the ball, deflecting it down and toward goal. Everybody else was reacting to that as McGinn controlled the ball without breaking stride, took another touch when faced only with Ben Williams in the Hibs goal, and then tucked it into the bottom-left corner.
Griffiths was the best player on the Easter Road pitch, dangerous every time he took possession and full of ideas. On another day he could have scored two or three. "I don't know how many shots he had but their keeper was fantastic, he made some great saves from Leigh," said Hibs manager Pat Fenlon.
McGinn had one chance to give up his disciplined role wide on the left and it worked for him. His manager will be happy to return him to these areas as soon as he can and when it was suggested to him that Aberdeen's win could be filed under "smash and grab", Craig Brown listed those who will return to give McGinn more ammunition in the coming weeks.
"We came to the team second in the league seven short of our best and lost another, Isaac Osbourne, during the game," Brown said. "So I think we should credit Aberdeen and not talk about smash and grab. We have Ryan Fraser out, who has become an important player, Gavin Rae, Stephen Hughes, who has dominated games, Gary Naysmith and Ryan Jack, another very good player."
Yesterday, those left standing scrapped out a win that cheered their rowdy travelling support, and despite the talent on the treatment table at Pittodrie, if he could keep one starter fit Brown would surely have to pick his sharp shooter.