"This decision had been made purely for the fact that I need to have a fresh start with my football. I need a new challenge and a new environment to feel really excited to play the game again,"the 26-year-old said.
"It’s been a pretty challenging few years with some ankle injuries and missing the grand final last year,"she said,alluding to her suspension during the 2018 season,which saw her miss the club's premiership win,and which she appealed,and lost,with the Human Rights Commission.
She called the move a hard decision,but"definitely something I have been thinking of for a little while".
Brennan,who captained the Bulldogs in 2017-18 and was co-captain in 2019,will join the Tigers for their debut in 2020 alongside fellow expansion clubs St Kilda,Gold Coast and West Coast.
She played 13 games with the Bulldogs over three years,including all seven in the 2019 season when the club won only two of their seven games and finished at the bottom of conference A.
As the inaugural captain of the Bulldogs'AFLW team,Brennan is no stranger to starting from scratch. She's keen to dive into it,joking,"I wanted to come in and start training this morning.
"I’m chomping at the bit to get out there,to get training and particularly to meet the VFL team and start to really slot into the structure and program here."