Marsh said he became so disillusioned with the so-called "Patriot Way" during his brief stint in New England that he considered walking away from the game, according to the San Francisco Chronicle.
"They don't have fun there. There's nothing fun about it," said Marsh to the newspaper. "There's nothing happy about it. I didn't enjoy any of my time there, you know what I'm saying? It made me, for the first time in my life, think about not playing football because I hated it that much."
Marsh, who was claimed on waivers by the 49ers in November following his release by the Patriots, admitted that he "wanted to get waived" because of how he was being utilized by New England.
A pass-rushing defensive end who was a fourth-round pick of the Seattle Seahawks in the 2014 NFL Draft, Marsh struggled mightily to adapt when the Patriots tried to shift him to outside linebacker.
"They asked me to do a bunch of stuff that I had never done: covering running backs and receivers and basically almost never rushing the passer, which is what I did in playing defensive line," said Marsh.
The ill-fated experience lasted nine games in New England for Marsh, who was acquired from Seattle for a pair of draft picks one week before the start of the 2017 season. He had 16 tackles and one sack while making one start for the Patriots.
Marsh told the Chronicle that he confronted Belichick after barely stepping on the field in a game versus Oakland and "kind of asked to get cut. ... I had confidence that I would have an opportunity elsewhere and I would take advantage of it."
The 49ers shifted the 6-foot-4, 245-pound Marsh, who played collegiately at UCLA, back to an edge rusher and he responded with two sacks and a team-high two forced fumbles in a reserve role over the final six games last season.
Despite the small sample size, San Francisco rewarded Marsh with a two-year, $7.7 million contract extension in February. He credited 49ers general manager John Lynch's confidence in him as the reason for re-invigorating his career.
"I used to play video games using him, and he was my favorite safety," said Marsh of Lynch. "So kind of having him show me love and tell me he wanted me here was incredible for me. He's one of the greatest safeties to play the game, and he's seen a lot of great defensive linemen."