Premier League champions Manchester United and big-spending Monaco have both been linked with a bid for the Italy international.
Marchisio, who is currently on Confederations Cup duty with the Azzurri in Brazil, stated he was 'proud' to have been linked with other clubs and suggested he would speak to Juve about his future.
However, Juve have no intention of letting the 27-year-old go and Marotta believes the new contract given to Marchisio last season is proof of his value to the Serie A title winners.
"We won't sell him," Marotta told calciomercato.com.
"It seems to me that the clearest demonstration about Marchisio's importance to Juventus was the contract renewal we signed in September 2012 until June 2017 which changed his salary.
"We would only review the situation if a sensational offer arrived that wasn't in line with the market and that, until this moment, hasn't arrived."