After Ronaldo had missed two great chances and spurned two other decent openings, substitute Varela struck an 87th minute winner to seal a 3-2 success over Denmark and get his side's Euro 2012 campaign back on track after their opening loss to Germany.
In the white of Real Madrid Ronaldo can seemingly do no wrong, scoring 60 goals in all competitions last season and generally giving the impression that he is unplayable.
But his form appears to have deserted him in Portugal's two Group B games to date in Ukraine.
Usually mentioned in tandem with Argentine Lionel Messi as the best in the world, the winger is still looking for the spark that Portugal need from him if they are to progress from what is arguably the toughest group in the competition.
Portugal's most capped player Figo said the team must improve their supply lines to Ronaldo but he has now taken 10 shots at Euro 2012 without getting his name on the score sheet. Only Russia's Alexander Kerzhakov has been more profligate in front of goal.
Leading 2-1 against the Danes in Lviv, Ronaldo had two gilt-edged chances to put the game out of reach.
He spurned both of them, first shooting straight at Stephan Andersen and then side-footing wide in a one-on-one situation from which he has scored dozens of goals in his career.
Instead, Nicklas Bendtner scored his second to level for Denmark, only for Valera, who has won just a handful of caps and plys his trade for Porto, to smash home the winner at the second attempt.
At the final whistle, Ronaldo looked more relieved than overjoyed.
His crossing was not much better than his shooting, embarrassingly ballooning one second-half effort out of play when he had found a sliver of space against Jacobsen.
More worryingly for Paolo Bento was Ronaldo's abdication of his defensive responsibilities - time and again Jacobsen raided up the flank, the Danish right back leaving the quicker forward trailing in his wake.
When Ronaldo finally did get his name noted by the referee it was not for a spectacular goal; instead he got himself an unnecessary yellow card in injury time for a petulant tackle.
Another yellow in the final group game against Netherlands on Sunday and he will be suspended for one match.
Goal-scorer Pepe was conciliatory about his captain after the game, telling reporters that Ronaldo "is one of the best players in the world, a very good captain and a very good leader. I'm sure he will score soon."
Valera, destined to play second fiddle behind Ronaldo and Nani in the national side, at least played his part.
