In an open letter to fans, Humphreys said he received an assurance from Marshall’s manager Martin Tauber that the New Zealand international would honour his current deal.
Reports in the media suggest Marshall is interested in taking up a lucrative short term deal to play rugby union in Japan.
“Let me put your minds at rest,” Humphreys told the Tigers official website.
“This will not be happening.”
“I have spoken with Benji’s manager, Martin Tauber, this morning who assures me that Benji is totally committed to his contract with Wests Tigers for the next three seasons.”