Goals from Mehdi Taremi and Moussa Marega propelled 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.
On a night when little went Juventus's way, Federico Chiesa's late strike at least handed them a lifeline going into the return leg in Turin on March 9.
Taremi pounced on a sloppy back pass after 63 seconds to fire in the opener, rattling Juventus who failed to create any meaningful chances before halftime.
Things got worse for Andrea Pirlo’s side when Marega blasted in Porto’s second 19 seconds into the second half.
Juventus eventually mustered a response when Chiesa fired in a precious away goal with eight minutes remaining, but it was not enough to stop the 2004 European champions from celebrating their first win over the Italian club at the fifth attempt.
"Up to the 70th minute we blocked out Juve, we did a good job defensively," Porto coach Sergio Conceicao told Sky Sport Italia.
"We knew we could create problems for them with a high press, blocking their strong points, and they have many.
"On a strategic level it was a good game, but we’re only halfway."
Chiesa's strike ended Porto’s run of five consecutive clean sheets in the competition and left the tie wide open.
"Our approach made the game an uphill struggle," Chiesa said. "We conceded a goal after a few seconds and in the Champions League when you’re not fully focused they will punish you. The away goal will give us strength for the second leg."
Juve impressed in the group stage by winning five games from six, including a 3-0 victory at Barcelona.
But they made a dreadful start when Taremi anticipated Rodrigo Bentancur’s pass back to Wojciech Szczesny and slid in to shoot past the goalkeeper from close range.
Juve were knocked off their stride by Porto’s pressing and were almost caught out again when Szczesny cleared the ball to Sergio Oliveira whose shot was deflected wide.
Matters got worse for the Turin club when captain Giorgio Chiellini limped off injured after 34 minutes.
Porto were even quicker out of the blocks in the second half as Marega got on the end of a Wilson Manafa cut-back to fire home within seconds of the restart.
Szczesny stopped an Oliveira shot from making it three, but the visitors came to life in the final 20 minutes.
Agustin Marchesin palmed away a deflected Chiesa shot, before the Italy international raced on to a pass and cushioned a finish into the corner.
The goal made Chiesa the first Juventus player other than Cristiano Ronaldo to score a knockout stage goal in the Champions League since Blaise Matuidi in 2018.
Ronaldo, the competition’s all-time top scorer, was largely quiet on his return to his home country, but he had appeals for a penalty waved away in stoppage time after going down under a challenge.
(Reporting by Alasdair Mackenzie, editing by Pritha Sarkar and Ed Osmond)