Pitino, who had hoped Dieng would return on Saturday from a broken left wrist, said the junior All-American likely won't return until Jan. 2 against Providence.
"Gorgui's latest exam with the doctor didn't go as well as my optimism was," Pitino said. "There's nothing setting him back. But it will be more than likely 4-6 weeks, rather than the three I was hoping for.
"The last X-ray we thought it would be healed, and it was not."
Dieng, who broke the wrist against Missouri in the Battle 4 Atlantis last month, participated in warmups last Saturday at Memphis. He has been going through some individual workouts and conditioning.
Pitino said Jan. 2 – the Big East Conference opener – "is the realistic goal. The good news is he is in great shape again. We'll be a little conservative with this one, conservative by my standards but not y the doctors."
Senior center Stephan Van Treese will be used "sparingly" against FIU after playing just nine minutes against Memphis. Van Treese has a bruise under his knee cap and needs some rest.
When asked about Russ Smith's ankle injury that occurred during the first half of the Memphis game, Pitino said "Russ is a faker."
"If he was playing great, Russ would not have limped off the court," Pitino said with a laugh. "You guys just buy that stuff – I know him very well."