Gillislee, 27, was released after falling out of favor in a crowded Patriots backfield. He was listed no higher than fifth on a depth chart that includes first-round pick Sony Michel, Rex Burkhead, James White and Jeremy Hill.
Hill and Gillislee were competing for a spot as a short-yardage back in the Patriots backfield, but the former Florida star struggled to make an impact during the preseason and was outperformed by Hill.
"Mike's doing fine," said Patriots running backs coach Ivan Fears, per Kevin Duffy of the Boston Herald. "He's staying healthy—remember last year he spent most of the training camp banged up. He's staying healthy, he's being productive on the field. Everything he's done has been very, very positive."
Duffy reported on New England's decision to release Gillislee.
Gillislee previously played with the Miami Dolphins and Buffalo Bills. He set career highs during the 2016 season in Buffalo, rushing for 577 yards and eight touchdowns. The Patriots signed him to a two-year contract last offseason, but he struggled with injuries and was largely ineffective when he was on the field.
The Saints were in need of running back depth as Mark Ingram serves a four-game suspension for violating the league's policy on performance-enhancing drugs. New Orleans released Jonathan Williams as part of its final roster cuts. Williams was initially expected to take over the Ingram role.
Gillislee will compete with rookie sixth-round pick Boston Scott for playing time.