Cristiano Ronaldo netted two penalties as Juventus out-classed Barcelona 3-0 at the Camp Nou to claim top spot in Champions League Group G on Tuesday.
It was Ronaldo's first meeting with Barca since leaving bitter rivals Real Madrid in 2018 and it did not take long for the forward to make his mark on the game.
The Portuguese tested Barca goalkeeper Marc-Andre ter Stegen early on, before opening the scoring from the spot in the 13th minute after being felled by Ronald Araujo.
Defender Danilo flashed an effort just wide as the visitors cranked up the pressure, with a stunning Weston McKennie volley putting the Italian champions two goals up and in full control seven minutes later.
"The defeat was because of how we played in the opening 25 minutes," a furious Barca coach Ronald Koeman said.
"We started badly, we looked scared, we weren't aggressive. It looked as if we'd come out looking not to lose, as opposed to trying to control the game. We weren't good, not even positionally.
"We got better but we lost the game in the first half an hour."
Both sides had already qualified for the knockout stages before kick-off. They ended the group phase on 15 points each but Juve took first place by virtue of a superior head-to-head record.
Ronaldo got his second penalty when Clement Lenglet was penalised for handball seven minutes after the restart.
Things almost got worse for the Catalans a quarter of an hour from time when Leonardo Bonucci thought he had scored, only for a VAR review to show he had been offside as he bundled the ball in from close range.
The result puts the under-fire Koeman under pressure, with the club suffering back-to-back defeats for the first time under his stewardship.
Forward Antoine Griezmann, however, said the defeat was not Koeman's fault.
"Who else's fault could it be other than the players? We're the ones who go out there and play," he said.
"We were missing everything: desire, attitude, a willingness to run. Everything was bad.
"We've left a really bad image here tonight, for ourselves and for the fans."
(Reporting by Joseph Walker; editing by Clare Fallon)
