"This was the most hard decision I have made during my time at Juventus", said Agnelli, who sat alongside Allegri in the press conference.
It was announced on Friday that Allegri would be leaving the Italian giants this summer despite an impressive haul of five consecutive Serie A titles.
However, despite domestic dominance, which also included four Coppa Italia titles, Allegri could not deliver European success, losing two Champions League finals - against Barcelona in 2015 and Real Madrid in 2017.
Allegri, 51, will say more today about why he is... His side were one of the favourites to go all the way this campaign following the mega-transfer of Ronaldo, though they were eliminated by Ajax in the quarter-finals.
"I leave behind a solid group with extraordinary players, both technically and as men, because you need good men to win as well as good footballers". It's fair to say that Allegri's successor has a hard task at hand.
Allegri ends his time with the club one year early, terminating his contract by mutual consent, bringing his five-year spell with the club to an end.
Instead, Juve relied on their resilience, flexibility, moments of individual brilliance from five-time World Player of the Year Cristiano Ronaldo and even, sometimes, just a lucky break.
"At the end of several reflections and analysis, we identified that this was the best decision to make", Agnelli said of Allegri's departure.
Allegri's final home match in charge with be Sunday's Serie A clash against Atalanta.
"It's been five years of wonderful love".
In attack, Ronaldo cost 117 million euros and winger Douglas Costa another 40 million, while at the back 40 million went on right back Joao Cancelo and 35 million on bringing back central defender Leonardo Bonucci from AC Milan.