Captain Ronaldo looked to have put Portugal ahead with a superb effort in the first half, the £80million man cleverly turning inside Gerard Pique before scooping his shot over Madrid club-mate Iker Casillas.
The effort was dropping into the net but Nani raced in from an offside position to head the ball in from point-blank range, leading to the goal being disallowed.
Reds man Nani said after the game: "I touched the ball because I thought I wasn't offside. Everything happened so quickly.
"After having time to think about it I apologised to Ronaldo. It was a great piece of play and I shouldn't have ruined it."
Ronaldo, who threw his captain's armband onto the pitch in anger after the goal was disallowed, felt the ball had already crossed the line before Nani got to it.
"I don't understand, even a blind man could see it was a goal, the ball was half a metre into the net," he said in Marca.
"I don't know if it's a coincidence or not but my best goals with the national team are being disallowed. I remember an overhead kick in the Bessa stadium which wasn't given."
Source: Manchester Evening News