Anelka will reportedly undergo a medical on Monday to allow the Shanghai Shenhua striker to sign a five-month deal, coinciding with the Chinese off-season.
Marotta told Sky Italia: "Anelka? In July we made some targeted investments, but now we are in an emergency situation in attack, so we moved to fix those issues, even if it is not official yet.
"It can be a good move for the short term, then at the end of the season we'll evaluate what must be done. He is filling a hole. It is a five-month contract with an option for the second season, if things go well.
"Anelka's arrival rules out any other transfers, because in this stage of the transfer window there are no other opportunities.
"He will put himself at the disposal of the squad and it'll be up to (manager) Antonio Conte to decide how to use him. After all, he is not in great physical condition considering he hasn't played for a month."
Juve will become the 10th club of a career which has seen Anelka rack up estimated transfer fees of almost £85million, while also scoring 14 goals in 69 caps for France.
He was part of their victorious Euro 2000 squad and has won the Champions League with Real Madrid, league titles in England with Arsenal and Chelsea and in Turkey with Fenerbahce and three FA Cups, two with Chelsea and one with Arsenal.