The Juve boss has been trying to explain the Bianconeri's recent quarter-final exit against Ajax. Juve were beaten 2-1 at home in Tuesday's second leg, meaning the Serie A giants still haven't won Europe's biggest prize since 1996.
The Champions League drought was supposed to be over once Juventus paid £99.2 million to sign Ronaldo from Real Madrid last summer. Yet Allegri believes the man who lifted the trophy in four out of the previous five seasons couldn't be expected to help Juve win by himself, per Peck:
"I always said that with the arrival of Cristiano Ronaldo, there was no mathematical assurance of winning the Champions League. Football is not a science.
"What's been written about Ronaldo confirms that his arrival at Juve did not guarantee us the Champions League.
"Look at Barcelona, who are back in the semifinals this year after four seasons and they've got Messi. There are lots of components to football.
"If we only win the league, it still means we've had a great season."
Allegri's assertion Ronaldo's first season in Turin can be judged a success simply by Juve retaining the Italian top-flight title is a bit of a stretch. For one thing, the Bianconeri have won the title the last seven years running, and can make it eight by beating Fiorentina at the Allianz Stadium on Saturday.
Juve's dominance of the domestic scene is almost old hat, and it was assured even without Ronaldo.
The latter was signed to deliver in the one competition all of the continent's big clubs want to win. It's the one competition he's made his own as a five-time winner with Real and Manchester United.
There's no other credible reason for Juve to have spent almost £100 million on a player who was 33 at the time of the transfer.
To his credit, Ronaldo did his bit, scoring six goals in nine Champions League matches, including in both legs of the last-eight tie against Ajax:
Yet for all his goals, the most dominant player of the tournament's modern era still couldn't help Juve take the next step. An ageing defence proved vulnerable, while a workmanlike midfield, featuring tough runners Blaise Matuidi, Emre Can and Sami Khedira, often lacked the guile needed at the highest level.
It would also have helped to have better support around Ronaldo in the final third. Mario Mandzukic is still a useful striker, but the 32-year-old target man isn't going to take many markers away from Ronaldo.
Perhaps the biggest letdown has been Paulo Dybala. The Argentina international has the flair and vision to keep Ronaldo supplied with chances, but he's also failed to jell with Allegri, missing the chance to capitalise on being played off the front and named captain vs. Ajax.
Naturally, the fallout from Juve's Champions League exit has raised immediate questions about Ronaldo's future. Italian publications La Repubblica and Gazzetta dello Sport (h/t Mark Jones of the Daily Mirror) reported Ronaldo is "furious" about the defeat and may leave after next season, despite having a four-year contract.
Arjun Pradeep @IndianRegista
🇮🇹 📰 | Front pages of Gazzetta, Corsport and Tuttosport headline on a Juventus revamp. Cristiano Ronaldo is furious & is waiting for reinforcements. CR7 remains the only guarantee for Juventus this summer. The club is already targeting to play the 2020 UCL final in Istanbul. https://t.co/e38MaZi2io
The idea Ronaldo will leave Juve early has been refuted by Allegri:
Allegri knows he needs Ronaldo if he and Juventus are finally going to make the grade in the Champions League. While thing haven't gone the prolific No. 7's way this season, he still knows no equal in this competition.
Fortunately for Allegri, history shows Ronaldo tends to respond well to setbacks at this level:
As long as Ronaldo remains in a Juventus shirt, the Bianconeri will still be major contenders for the trophy. However, Ronaldo's presence alone can't be allowed to breed complacency.
Allegri and the Juve board need to invest in more marquee talent this summer.