Fabio Capello described it as "a serious blow" as Juventus were knocked out of the Champions League before the knock-out phase.
The former Juventus, Roma and Milan head coach said Massimiliano Allegri's team lacked spirit and fight as they went down 4-3 at Benfica, with two late goals for the Italians serving only as pitiful consolation.
Juventus, who have just one win from five games, could yet finish bottom of Group H, as their last opponents are mighty Paris Saint-Germain who are battling with Benfica for top spot.
Should Juventus lose that one, and Maccabi Haifa take even a point from their home game with Benfica, the Turin giants will sink to fourth place and miss out on the Europa League.
Speaking on Italian channel Sky Sport, Capello said: "Allegri lacked the players on whom he founded this team, but they did not show character and determination.
"Even if they do not have these players, they must always demonstrate who Juve are, a team that never give up, want to fight, and tonight they didn't show themselves as they have in the past."
Capello added, according to Tuttosport: "This is a serious blow, you have to start from this moment with everyone together. I don't seem to see this spirit."
The 76-year-old, who also coached England, Russia and Real Madrid in his storied career, said Juventus were simply sluggish compared to the pace they need to play at.
"Juve are always under pace even when they win in the league," Capello said. "They win because at that moment they have better players than the opponents. When they have found players of equal or superior quality, this is the result."
Juventus will be absent from the last-16 stage for the first time since the 2013-14 season, and their points tally is the lowest they have managed after five games of any previous Champions League campaign where they have featured.
Capello found praise for teenage substitutes Samuel Iling and Fabio Miretti, however, commending them for showing purpose and quality.
"At this point, Juve must think about recovering in the league," Capello said, with Juventus sitting eighth in Serie A, "but they have players who may be ready for the future."