Collingwood rebounded from a goalless opening term with a barnstorming second half which saw it kick nine goals to three to run out 12. 10. (82) to 8. 8. (56) winners at the MCG.
Cox finished with a career-high 21 disposals and eight marks while also kicking a goal, with his aerial dominance a throwback to his famous 2018 preliminary final performance.
However, despite the Magpies' dominant second half, it was Melbourne's Clayton Oliver who was selected as the best player on the park after picking up a game-high 43 disposals.
Two of the three voters on the three-man panel, AFL greats Matthew Lloyd and Cameron Ling, selected Cox as their best on ground, giving him six votes. However, the third voter, AFL.com.au reporter Josh Gabelich, did not have a single vote for Cox, instead awarding his 3-2-1 to Oliver, Nick Daicos and Brody Mihocek.
The snub was enough to give Oliver the nod with his total of seven votes narrowly edging out Cox's six.
Following his stunning performance, Cox explained how being able to play more minutes in the ruck in the absence of star big man Brodie Grundy had helped him string a number of strong games together.
"Being able to play a bit more ruck, you get a bit more of an opportunity to get your hands on it in the middle, so you get a bit more confidence," he said.
"Sometimes in the forward line you can get stuck on your own and don't get the ball for a bit and then you have to make the most of every opportunity. Being in the middle now, it opens up a bit more of an opportunity for myself."
The loss is Melbourne's third straight and caps a week from hell following the brawl between Steven May and Jake Melksham at a popular restaurant.
The reigning premiers will head into the bye in second spot on the ladder, trailing Brisbane on percentage, while Collingwood remains in eighth spot.