The 25-year-old will notch up the century in his first finals game after seven seasons with the Lions.
Brennan said he habn't thought about the milestone as he prepared for the biggest game of his career.
"I would probably prefer to play my 100th during the season because it's not really about me at the moment, it's about the team," he said.
"We'll be on holidays on Monday or they'll (Carlton) be on holidays on Monday – it's as simple as that."
Brennan was drafted by the Lions with pick three in the 2002 NAB AFL Draft.
While dazzling fans with his skills in his early days, Brennan couldn't manage a finals game despite the Lions advancing to the 2003 and 2004 grand finals.
"It was a very hard team to crack into back then," he said.
"Injuries didn't help me out either, but it's definitely a good opportunity now to play my first final – and at the Gabba is even better."
Finding a balance between keeping his natural flair and following team structures is a constant battle for the talented ball player, known for his one-handed marks and freakish goals.
"It's really hard to find a balance," Brennan said.
"If I'm playing full-back there's really no room for it."
"Full-forward you can get away with a little bit more but it's a very disciplined game now, so you make one mistake and good oppositions hurt you."
Brennan has played just about every position on the field this year, filling in at full-back against Port Adelaide in round 21 when Daniel Merrett went down injured and picking up 16 hit-outs in the ruck against the Swans in round 22.
"This week depending on what lineup we go it could be full forward, could be ruck, could be back; I just don't know until the day," he said.
"It doesn't bother me. Wherever the team needs me I think is where I'll play and where I'll try and adapt to the best of the team's needs."
Brennan stressed the need for a high pressure game against Carlton, which has won its last two games at the Gabba, both by six points.
And after seven years of waiting, he's eager to taste finals action.
"We're trying to create our own little dynasty here at the moment," Brennan said.
"It's uncharted territory for me so I'm just itching to get out there."
