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When Juventus president Andrea Agnelli flew out to the city of Kalamata in Greece three years ago to woo Cristiano Ronaldo it was not on the expectation of continued dominance in Serie A.  

Juventus had won seven consecutive league titles by the time Agnelli boarded the private jet to meet Ronaldo on his post-World Cup holiday.  

No. Agnelli and Juventus were only ready to flex their financial muscles in pursuit of one thing: the Champions League. In their mind Ronaldo was money, Mr Champions League at Real Madrid. They wanted his magic touch in Turin and yet so far no rabbit has been pulled from his hat.  

© Provided by Daily MailCristiano Ronaldo is tasked with salvaging Juventus' season in the Champions League last-16

© Provided by Daily MailThe future of Andrea Pirlo (left) and Ronaldo (right) will be scrutinised if they exit to Porto

There's a saying in Italian that reads a mali estremi, estremi rimedi - desperate times call for desperate measures. 

Against Porto on Tuesday night, down 2-1 after a dismal first leg, Ronaldo needs to breathe new life into the Old Lady because chances are running out. Juventus are desperate and with hopes of going ten-in-a-row in Serie A fading fast, this is it. 

It is, without hyperbole, a season-defining night for Ronaldo and Juventus. To some this will be legacy defining for his time in Italy. The stakes could not be higher.  

'These are Cristiano's games, he's always proved it,' boss Andrea Pirlo bullishly told reporters on Monday.   

'He followed a special training program these days, he is serene and is looking forward to playing.' 

Exits to Ajax and Lyon were scarring. Both were ties Juventus were favourites in and yet the barren run without Champions League success, now in its 25th year, rumbled on.  

Ronaldo scored both of Juventus goals over the two legs against Ajax; they lost 3-2 on aggregate. He also scored both of Juventus' goals against Lyon; they were eliminated on away goals with a 2-2 aggregate score. 

Those exits hurt. There were tears, recriminations, interviews were abandoned and his family proved the mouthpiece for his frustrations. 

Ronaldo was left in tears in 2019 when Juventus were knocked out at home against Ajax

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'He was very sad. He would have liked to have gone to the final,' his mother Dolores Aveiro told Gazzetta dello Sport after the exit to Ajax. 

'What did he say to me? "Mom I don't make miracles".' 

There was a similar feeling last season when his brace at home to Lyon proved to be in vain. This time it was his sister Elma that condemned the tools around her brother. 

She wrote on Instagram: 'You did better than anyone. I am proud to see you play, and to see your dedication, but unfortunately alone you cannot do everything, moreover it is impossible!!!!! 

'You know football is like that, but you also have to think you did your best, and you're still the best.' 

But the help has never really arrived. Still the burden of responsibility rests on the shoulders of Ronaldo, even at age 36.

This season Ronaldo has 27 goals to his name. Alvaro Morata has a respectable 16 goals while the rest of Juventus' squad has combined for just 32 goals.

© Provided by Daily MailRonaldo was a figure of frustration in Porto but he is said to be 'fired up' for the second leg

© Provided by Daily MailFront pages such as Tuttosport on Tuesday described the second-leg as a final for Juventus

Against Porto it was Federico Chiesa who got the vital away goal, Ronaldo denied a penalty in the last second to steal the headlines. On Tuesday night a 'fired up' Ronaldo needs to make the telling contribution.  

'Cristiano is always ready to play these games,' team-mate Leonardo Bonucci said. 

'Some time ago, he said he would play only Champions League games. So, you can imagine his energy for tomorrow's game.' 

Rested for the weekend visit from Lazio - which Juventus won 3-1 as he came on as a late substitute - it was the clearest sign yet that Ronaldo's eyes are now firmly locked on the Champions League. Ten points adrift of Inter Milan in Serie A, it's now or never in Europe. 

There is also the financial dependency on the Champions League and the £9.5m Juventus will receive from UEFA if they progress. 

Like a boxer stumbling but staying on their feet, Agnelli is doing his work to keep Juventus stable amid the financial turmoil of the Covid-19 pandemic but there would be no disguise of the damage done on the company accounts for an early exit.

Ronaldo and Matthijs de Ligt, both among Juventus' top earners, may be seen as available this summer if they are eliminated to Porto and Agnelli is forced to cut the fat from the accounts. A lot is up in the air in the hours preceding tonight's game.  

© Provided by Daily MailRonaldo (second left) pulled a rabbit from a hat at this stage in 2018-19 against Atletico Madrid

© Provided by Daily MailAndrea Agnelli moved heaven and earth to get Ronaldo but so far it has not brought the trophy

There are a number of similarities to the last-16 tie in his first season at Juventus against Atletico Madrid. 

Diego Simeone's Atletico won the first leg 2-0 in Spain and it fell to Ronaldo to salvage the tie. 

Sportsmail went to Turin to witness an incredible game in which Ronaldo produced a devastating hat-trick to send Juventus through. It was, to date, his finest night in a Juventus shirt. 

That was Operation Cristiano Ronaldo in all its glory as Agnelli beamed from his director's box at the Allianz Stadium. There will be no fans to drive Ronaldo and Co on on Tuesday but this last-16 tie is much the same, at least in the level of significance. 

Come 9pm local time there will be a collective intake of breath in Turin. Win and the inquest will be put on hold. Lose and the 'project' Agnelli outlined to Ronaldo in Greece may have run its course with three coaches failing to find the solution.  

'I work day by day, I know my project and the club's project,' Pirlo said, asked if defeat would bring his time in charge to an abrupt end in his first season.

© Provided by Daily MailHe needs a repeat here with Juventus' season on the brink of collapse if they are eliminated

'This game is like a final for us. We need to turn the tie around. It's an open result and we must be clear-minded.

'We watched the first leg many times. We had planned to play differently. We made a mistake at the beginning of the game, and the match changed.' 

The front pages in Italy carried just one word when it came to Juventus on Tuesday: final. 

There have been a few of those since Ronaldo arrived and twice now his co-stars have had stage fright. Freeze once more and who knows if there will be another chance for Ronaldo to guide the Old Lady to the finish line?