Benfica are in Turin defending a 2-1 lead in their semfinal.
"I trust (Antonio) Conte and all the older players like Buffon and Pirlo," Vialli told Uefa.com. "But the other players must improve in Europe, especially in terms of confidence.
"Winning the Europa League could be crucial in helping Juve to start playing better in the Champions League.
"It would certainly be a good way to gain belief and knowledge. It worked for us."
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