Juventus' involvement in the 2020/21 Champions League could come to an end sooner than most anticipated.

On Wednesday night, the Bianconeri suffered an unexpected 2-1 loss at the hands of the FC Porto in the first leg of their last-16 tie.

Things could have been even worse for Andrea Pirlo's side, as the hosts created plenty of chances after Mehdi Taremi and Moussa Marega had put them 2-0 up.

They couldn't capitalise on their advantage, though, and Porto were made to pay in the 82nd minute as Federico Chiesa scored what could turn out to be a massively important away goal.

Juve will now fancy themselves to turn the tie on its head when they meet in Turin, but the team - Cristiano Ronaldo in particular - will have to perform a lot better for that to become reality.

Pirlo's men were woeful for 99% of Wednesday's game and Ronaldo dropped one of his worst ever Champions League displays.

The 36-year-old has scored goals for fun in 2020/21, but his showing in Porto was well below the lofty standards he has set throughout his glittering career and it has naturally attracted criticism.

Italian legend Antonio Cassano is one of the outspoken critics and he has slammed Juve's talisman, stating that he does not fit in with Pirlo's managerial ideas.

“I have always said, considering that he’s a phenomenon and has scored a billion goals, that it could be difficult with Pirlo’s idea of football,” Cassano told Bobo TV, per Football Italia.

“He scores a goal per game, it’s true, but struggles with the ideas of Andrea. He has always been a bit selfish, he doesn’t care about others scoring goals, he’s the kind of player who lives to score.

“He doesn’t live for the play, the great match, he lives for the goal and at this moment, the situation is getting worse.

“Years go by for everyone and he is having difficulties. Juventus are trying to change their ideas and play a different type of football, due to the qualities of Ronaldo.”

It's a bold statement by Cassano, especially when you consider that the Portuguese has basically carried Juve most of the time during what's been a tough season for the Italian champions.

Ronaldo has scored 23 goals in 25 games in all competitions, with 16 of those strikes coming in just 18 Serie A appearances.

Yes, he has a tendency to be selfish at times, but that's why the five-time Ballon d'Or winner is football's record goalscorer and one of the greatest players of all time.

Juve have serious issues that need resolving, of that there is no doubt. Ronaldo isn't one of them, though, and his display versus Porto will almost certainly end up being viewed as simply a one-off.