Marshall starred in his first game back for the Tigers in Saturday's upset win over the Sydney Roosters, his first game for the club since leaving for Super Rugby club the Auckland Blues at the end of 2013.
It was originally understood Marshall's departure came about following a contract dispute over a potential extension at the club, but the playmaker revealed on Sunday he was left unwanted by the Tigers' previous administration.
"At the time Mick Potter was the coach and the club said to me that I wasn't going to be in the plans for the future," Marshall told Triple M NRL.
"It's hard for me to be somewhere where I don't feel wanted and I just wasn't feeling that.
"Obviously at the time I didn't want to go to another NRL club because my heart was with the Tigers so that's why I ended up going to rugby union."
Marshall is one of just four players to have played more than 200 games for the merged club, and is still the most famous player to have turned out for franchise.
His latest signature already looks likely to pay off, with regular five-eighth Josh Reynolds expected to be out for up to a month with a hamstring injury.
Regardless, Marshall said Potter's decision had worked in his favour as it had since prolonged his career.
"It's not something I regret because if I didn't leave I probably would have retired a lot earlier from getting too comfortable there and a bit complacent and just feeling a bit lost the last couple of years there," he said.
"I was able to find a bit of myself again, the reasons why I play footy, enjoying the game.
"When something gets taken away from you and it gets given back you appreciate it a bit more."