Goals from Mehdi Taremi and Moussa Marega propelled FC Porto to their first ever victory over Juventus in the Champions League after they secured a 2-1 win over the Italian champions in the first leg of their last 16 tie on Wednesday.
Mehdi Taremi pounced on Rodrigo Bentancur's poor back pass to slide in and convert after only 63 seconds.
Juventus were being outplayed but Adrien Rabiot saw an acrobatic effort pushed away, and Moussa Marega stroked home 19 seconds into the second half.
But Federico Chiesa pulled a goal back on 82 minutes heading into the return leg of the last-16 tie on 9 March.
Juventus have dominated Serie A, winning the title for the past nine years, but Andrea Pirlo's side are off the pace this season at home and could not come to terms with an energetic and lively Porto outfit either.
The Portuguese champions pressed from the first whistle and got an immediate reward as Bentancur's pass under pressure fell short of Wojciech Szczesny allowing Iran international striker Taremi to sneak in and score.
The second half started in similarly calamitous fashion, Wilson Manafa picking out Marega unmarked eight yards out to slip home a finish at the near post.
Porto, winners of the competition under Jose Mourinho in 2004, last reached the quarter-finals two seasons ago and were strong favourites to reach the last eight with eight minutes remaining.
But although Cristiano Ronaldo was kept quiet, Italy international Chiesa broke from midfield and side-footed in a neat finish to give Juventus an important away goal.
"We prepared for the game well, differently from how it was during the match," Pirlo told Sky Sport Italia.
"That wasn't the attitude that we wanted to impose, but when you go down a goal after a minute it gets harder.
"We knew that they close up the spaces very well, it was the match that they wanted to play, and we handed it to them on a silver platter."
Porto coach Sergio Conceicao said his side will not send his team to Italy simply to hold onto their slender advantage in the second leg.
"We need to be rigorous defensively, it'll be a different game," Conceicao said.
"Juve need to perform a comeback, but that doesn't mean we will go there just to defend. We'll see who will play, if the characteristics of the players are different."
Meanwhile Erling Braut Haaland continued his stunning scoring run in the Champions League as Borussia Dortmund put aside their domestic woes to take control of their last-16 tie with Sevilla.
Mahmoud Dahoud levelled before Haaland got his 17th goal in 13 games in the competition to put them ahead.
It was 18 soon after via a neat finish, with Luuk de Jong scoring late on to give Sevilla hope in the tie.
The substitute's side-foot finish from a free-kick was reward for a concerted push from the home side that ultimately came too late to level the score on the night.
There was a video assistant referee check for a penalty for the Spanish side in added time for a potential foul by Thomas Meunier on De Jong but the officials deemed the contact between the two legal.
The second leg in Germany is on 9 March.