Ronaldo was left incensed during the World Cup qualifier between the two nations when he had a goal controversially disallowed.
The Portugal captain threw his armband to the ground and stormed off the pitch in frustration at the decision, earning himself a yellow card for dissent.
With the scores level and Serbia a goal down, Ronaldo prodded home – only for Serbia keeper Nikola Milenkovic to track back and scoop the ball from the line.
Replays showed the ball had crossed the line before Milenkovic’s intervention, but the lack of goal-line technology meant officials missed it, leaving the Portugal team fuming.
Fernandes picked up a booking in the match, which rules him out of Portugal’s clash with Luxembourg on Tuesday.
The United star travelled back to Old Trafford in the meantime and was greeted by a prank courtesy of his Serbian team-mate Matic.
Taped to Fernandes’ locker was a picture of the controversial incident, but with the goalline moved inside the net.
Matic tagged both Ronaldo and Fernandes in an Instagram picture of the prank.
Alongside it, he wrote: “Just on the line. Is it all clear now?”