Juventus overpaid to sign Federico Chiesa from Fiorentina in the summer transfer window, according to Claudio Marchisio.
Juve paid Fiorentina an initial loan fee of €10 million (£9m/$12m) for Chiesa on October 5, with an option to buy for €40 million (£36m/$47m) included in the final agreement between the two clubs.
The 23-year-old rose through the youth ranks at Artemio Franchi Stadium before stepping up to the senior squad in 2016, and went on to score 34 goals in 153 games for La Viola.
Ten of those efforts came as he helped Fiorentina avoid relegation last season, and Juve were impressed enough to hand him a temporary two-year contract at the Allianz Stadium.
Chiesa's move to Turin will automatically be made permanent if he plays a minimum of 60 per cent of the club's fixtures during that period for at least 30 minutes, while he will also have to contribute a minimum of 10 goals and 10 assists.
The Italy international has made a bright start to life with the Bianconeri, with Andrea Pirlo handing him six starts in the early stages of the new season, but Marchisio thinks his old club were wrong to invest so heavily in the winger.
"It's not right that someone who was fighting relegation should cost €50-60m," the former Juve midfielder told Gazzetta dello Sport.
"He is a real talent, but there is too much pressure on him created by the transfer market.
"He needs to find the right position on the field, but in my view, he will explode and become a star."
Chiesa played the full 90 minutes of Juve's 2-0 home defeat to Barcelona in the Champions League on Wednesday.
Pirlo stressed post-match that his rebuilding project will take time, but also admitted his side must continue to deliver consistent results while trying to adapt to a new style of play.
"Maybe we will need a bit more time, but we have to know that results must come through a certain type of playing style that maybe we are struggling to assimilate," he told reporters.
Juve are due back in Serie A action away at Spezia on Sunday, where they must win to close the gap on league leaders AC Milan before their focus shifts to another Champions League group stage outing against Ferencvaros.
