Vidal has been strongly linked with a move away from Turin in recent months with Manchester United reported to be among the top clubs keen to acquire the 27-year-old's services.
Allegri told La Gazzetta dello Sport: "He (Vidal) is like a caged lion. He would like to play, but he needs to train more. Arturo has a great spirit.
"It is normal that there are rumours about him: the great teams search for the great players. But Vidal is already in a great team."
And Allegri has targeted two more signings as he looks to strengthen his squad before the start of the Serie A campaign.
The Italian champions have already brought in Patrice Evra, Alvaro Morata and Kingsley Coman on permanent transfers this summer, while Udinese winger Roberto Pereyra joined the Turin giants on loan.
But Allegri, who replaced departed Antonio Conte at the helm earlier this summer, believes his team still needs further improvements.
"We need two more signings," he added. "But they have to be quality signings. We need a defender and a striker.
"It's useless to give names as acquisitions depend on who you can bring in and who is on the market.
"We have little time to act and we must choose carefully. We cannot afford to make any mistakes regarding these two signings."
On the arrival of Evra, Allegri added: "He's working hard, with a load he was not used to. He needs time to get accustomed to Italian football and these coaching methods."
Allegri also wished his predecessor Conte good luck with the national team, saying: "It was the right choice for the Italian national team. I wish him good luck. I hope he'll do well, Italy really need it."
Juve begin their Serie A title defence against Chievo in Verona on August 30.