Ravanelli, who won the Champions League with Juventus in 1996, spoke to La Gazzetta dello Sport about the club's attacking struggles this season.
"It was a negative season for David. He has scored some goals, but I don't think he's a player you can rely on to win Champions League titles or Scudetti."
"He has paid a high price for the leap in quality. Playing at Lille — in a league without too much pressure, in a team that plays automatically — is one thing. Making the difference at Juventus is another. The weight of the shirt is much more difficult to bear. You need great personality. The difference between a champion and a good player nowadays lies in personality, character and determination. You need to have these qualities to play at Juventus, or you'll struggle."
Ravanelli was similarly critical of Belgian striker Openda, who joined from RB Leipzig last summer.
But he also is insisting Edon Zhegrova deserves another chance.
"Zhegrova has much more personality than David and Openda, who have always given me the impression that they don't want to take on too many responsibilities."
He was more generous toward Kosovo winger Zhegrova.
"I would give him my trust. I'd love to see him in a positive Juventus side, with a winning mentality. He's someone who embraces responsibility — not someone who, after failing one dribble, shies away from trying another."
Zhegrova has made only one start in all competitions this season, though a groin injury at the start of the campaign severely disrupted his preparation. The club is understood to be assessing whether to sell him in the summer, with a minimum fee of €11.4 million needed to avoid a balance sheet loss.
David has scored eight goals across all competitions — third at the club behind Kenan Yildiz and Weston McKennie. Openda has been the bigger disappointment, contributing almost nothing of note since Luciano Spalletti's appointment.