The 33-year-old, who joined the Lions on loan from Queens Park Rangers last summer, has not scored a single league goal in 11 appearances.
"He is under contract with us for the next week and if called upon, he will play. I would say, though, that if people stay fit, it is unlikely he will play. I think in terms of going forward, it is time to go with other strikers," Jackett told Sky Sports News.
"I have been pleased with what Rob has done for us, he has been in teams that have earned us points and got us through rounds of the FA Cup.
"Perhaps he has not converted some of the chances he has had but his presence and experience has been there. I thank him for what he's done but I'm looking for a fresh combination up front. He understands and agrees with that decision."
Millwall have lost each of their last three games.