Lescott has lost his place in the heart of the Manchester City defense, despite being an England regular, with Mancini often preferring to select Serbia youngster Matija Nastasic as Vincent Kompany's partner at center back.
Kolo Toure was called upon ahead of Lescott to replace the injured captain earlier in December but with the Ivorian due to leave for the Africa Cup of Nations next weekend, Mancini is adamant that Lescott is not for sale.
"We can't sell players," Mancini told reporters when asked about the former Everton man's future. "We won't have enough to play if we sell."
The Italian has also suggested that out of favor striker Mario Balotelli will remain at the Etihad Stadium despite reports linking the 22-year-old with a January departure.
Lescott has been linked with a return to Goodison Park having made only seven league starts this season.
That tally is in stark contrast to City's last campaign, when he established himself at the heart of back four by making 33 appearances in the top flight.