Juventus have it all to do in their Champions League last-16 tie against Porto.Andrea Pirlo's side travelled to Portugal hoping to get a positive result.But they turned in a poor performance as they were beaten 2-1.It all started horribly for the Turin-based side as a catastrophic error from Rodrigo Bentancur handed Porto the lead after 61 seconds.They were 2-0 down 20 second after half-time as Moussa Marega found the net.Cristiano Ronaldo in action for Juventus vs PortoFederico Chiesa scored a vital away goal late on for Juventus but, despite that goal, they will be very disappointed with their display.In truth, they were extremely poor. They deserved their defeat and they are perhaps fortunate they are only one goal down going into the second leg.Cristiano Ronaldo was particularly quiet. It wasn't the Portuguese legends' night as he often cut a frustrated figure.And one moment that would have made him even more frustrated occurred in the 61st minute.With Juventus two goals down, Ronaldo skipped over a challenge and ran at Porto's goal.But his run was stopped by none other than his own teammate, Alex Sandro.The Brazilian defender blocked Ronaldo, allowing a Porto player to take possession back.

That's just comical.

Tancredi Palmeri, beIN Sports correspondent, tweeted the video and it has gone viral, accumulating over 5k retweets at the time of writing.

Pirlo expressed his disappointment at his side's performance in his post-match interview.

"Porto have often played like that in the Champions League but we allowed them to play the way they wanted. We had to move the ball quicker and better," he said, per Uefa.com.

Alex Sandro in action for Juventus vs Porto

"Porto were closing spaces in the middle and we had to use the flanks more. It's not easy, however, when the ball does not move quickly enough."

Juventus will need to be much better when they welcome Porto to Turin for their second leg next month.

If they perform like they did on Wednesday evening, there's no chance they make it through to the quarter-finals.