The 20-year-old Norfolk-born back initially signed with the black, green and gold in the summer of 2020, having come through the club’s Academy system.
Having previously represented Norwich School and Holt RFC, Long-Martinez featured heavily for Saints’ Under-18 side during the 2019/20 season, top scoring across the Academy
League campaign, and at the 2019 Premiership Rugby 7s competition, prior to signing a full-time deal at cinch Stadium at Franklin’s Gardens.
He scored his only Saints try in a pre-season friendly against Worcester Warriors ahead of the 2020/21 campaign, and gained experience out on loan with Championship side Bedford Blues over the last two seasons.
A Saints statement read: "Northampton Saints would like to wish Dani well for the future as he looks to pursue a different path, and thank him for his contribution during his two years at the club."