The five-time Pro Bowl receiver, whom the Giants signed last offseason to a two-year, $11 million deal, never seemed to get comfortable and was struggling before suffering a left ankle injury in Week 5 that required season-ending surgery.
Marshall had a cap hit of $6.2 million for the 2018 season, which would have been the seventh highest on the team. The Giants will save $5.156 million by releasing him. According to NFL Players Association records, the team was $4.9 million under the cap as of Thursday morning.
Gettleman was asked whether the move meant the Giants were interested in signing wide receiver Dez Bryant, whom the Dallas Cowboys released earlier this week and who has expressed interest in signing with an NFC East opponent of his former team.
Said Gettleman: "We are interested in everybody."
Marshall finished last season with 18 catches for 154 yards and didn't score a touchdown in five games -- all career lows. The Giants also lost star receiver Odell Beckham Jr. for the season in Week 5.
The 34-year-old Marshall had been consistently working out at the Giants' facility since the injury. He wanted to return to the team and doesn't seem to have an intention of retiring.
"I'm all-in on football," Marshall said late last season. "I've rebuilt my body. I think I'm two great years away from, and I'll say it, I want to be a Hall of Famer and I think I got two great years to go to be mentioned with some of the greats.
"I'm not just playing this game just to be a guy. I want to be remembered for the product that I put out on the field. So these last few years have been tough -- last year with the Jets, this year with the Giants -- but I'm hopeful that the next couple years for me will be some amazing years and some of my best work."
The once-outspoken veteran tried to play a different role with the Giants last season, attempting to serve as a resource and mentor. Embattled cornerback Eli Apple said he had conversations with Marshall throughout the season.
He has 959 catches for 12,215 yards and 82 career touchdown grabs. He is 16th all time in receptions -- only 23 behind Hall of Famer Randy Moss -- and is just inside the top 25 in yards (23rd) and touchdown catches (23rd).