Brennan may miss the Lions' round three clash with Port Adelaide at AAMI stadium after being charged with bumping Carlton ruckman Matthew Kreuzer.
He faces a two-match ban, and even with an early guilty plea would cop a one-match suspension due to his poor record at the tribunal.
The ban would spare Brennan from returning to the scene of an ugly headbutting incident involving Port Adelaide tagger Josh Carr at AAMI stadium in round 14 last year.
Port went on to win that game by 48 points after booting six goals to nil in the final term.
Brennan received a one-week ban for that incident, but Lions assistant coach Adrian Fletcher said Brennan has evolved into one of the club’s senior players.
“He’s a mature man, he’s a leader of the footy club, he understands that you have to play inside the rules and the boundaries,” Fletcher said.
“We’re pretty disciplined as a group. Vossy instills it into the guys week-in week-out.
"If you go outside the boundaries, you are either going to get reported or give away free kicks which will cost us the game in the end.”
The Lions have a readymade replacement in Tom Rockliff, who kicked five goals and gathered 40 possessions in the reserves last weekend.
“That’s probably the best game you can have as a midfielder,” Fletcher said.
“He probably only missed out on the first game because we had 27 players all fighting for that last spot.
"He’s gone back to the reserves level and showed that he’s an elite player and he deserves his chance when he gets it.”
The Lions are again sweating on the fitness of Jed Adcock, who will have scans on a strained quad on Tuesday.
Fletcher said the Lions players have recovered well from a five-day break leading into last Thursday night’s game against Carlton.
He said they lacked energy at the stoppages, with the Blues dominating clearances 49 to 29, but that a nine-day break will help freshen them up for the challenge of playing the undefeated Port Adelaide on their home turf.
“Port seem to get themselves up for Brisbane,” Fletcher said.
“They always get off to a really good start against us. It’s really important that we take the crowd out of the game so we need to kick some goals early and give our guys the confidence.”
