The midfielder had expected to sign for Juventus last week.
"Finding a suitable replacement a few hours before the transfer market closed was an almost impossible task," director general Maksim Mitrofanov told Itasportpress.
“The club intends to extend his contract," insisted Mitrofanov. “If he does leave, it will be purely down to his decision. We already formulated an offer, which the player appreciated.
“For the moment we only know that Witsel does not intend to move from here until his contract expires. He is a professional, so regardless of a renewal, we know that we can count on him to the end."