The Spain international arrived in Turin on a free transfer from Athletic Bilbao in the close-season.
Having initially struggled to make an impact, speculation has since mounted that Juventus may look to cash in on the 28-year-old in the new year, with Premier League table-toppers Arsenal touted as a possible destination.
But Llorente has showed signs that he is starting to settle in Italy, including scoring the equaliser in Juve's 2-2 draw with Real Madrid in the UEFA Champions League on Tuesday, and Marotta is confident that he will continue to improve.
"The player (Llorente) is not for sale," he told Tuttosport. "He's never been available.
"He will stay here with us. There is great faith in the boy and he is reaching his peak condition.
"We're very happy with him and his progress."
Llorente has scored once in eight Serie A appearances for the reigning champions, with Juventus occupying third spot.
‘It was without a doubt one of the most important matches that I played in my career. It wasn’t just Champions League football – it was a whole club at stake’: Ex-Chelsea star opens up on key game which changed the Blues' fortunes forever
'I was Arsenal captain and really enjoyed it, but when Man City come calling, you have to listen': England international reveals reason for swapping London with Manchester
