The Nets tried to trade Jack but were unable to do so.
They had a Thursday deadline on Jack's $6.3 million team option, of which just $500,000 was guaranteed.
The Nets are on the hook for that $500,000 partial guarantee unless another team claims Jack off waivers. Brooklyn can stretch that $500,000 out over three seasons to save some additional cap space.
The 32-year-old veteran averaged 12.8 points on 39.1 percent shooting in 32 games last year before his season was cut short by an injury to his right ACL.
The rebuilding Nets have a need at point guard in free agency and are interested in Jeremy Lin, who is himself interested in the Nets, according to multiple sources. Lin developed into an overnight sensation in New York after working with then-Knicks assistant Kenny Atkinson, who is now the Nets head coach.
Brooklyn has been linked to former NBA player Sergio Rodriguez, who has been playing for Real Madrid.