Cynicism, the Dublin defender insists, you can't banish quickly or punish harshly enough, but as a paid-up member of the defenders' union, Brennan is fearful the cause could have wider-reaching consequences on the legitimate rough-and-tumble.
"They're always trying to change the game around, aren't they? What's wrong with it?" Brennan, the Dublin footballers' representative at the launch of the Spring Series, stressed in Croke Park yesterday, warning that the constant tinkering of legislation has before, and will once again, "over-complicate it for the players and for the referees".
Brennan is not, he maintains, a subscriber to 'the dark arts', qualifying his pro-physicality stance by suggesting: "some of the cynical stuff like time-wasting and lads pulling each other down with rugby tackles... something needs to be looked at there."
But to him, whether by design or byproduct, it's a case of further thinning out the legitimate aggression and confrontation, facets which were once held aloft as some of football's most endearing qualities.
"You can't look at a fella now sometimes without getting booked," he lamented before nodding ruefully across the room at the Dublin hurlers' representative at the same function.
"I look at the hurlers and Johnny McCaffrey there and they very much tear into each other and they get on with it.
"But football has gone a bit like basketball at times and how often do you see a fella hit a fella on the shoulder and there's not a free? They are taking the physicality out of the game in my opinion.
"Whatever about the pulling and dragging," he continued, "I think that needs to be stopped, certainly, but in regards to a lad giving a good shoulder thump, what's wrong with that? Many referees are blowing up for that and they're giving rash bookings. A big hit is a part of the game."
And a part of the game in which Brennan has excelled in recent seasons at the fulcrum of the Dublin defence under Pat Gilroy, too.
Naturally then, a new manager has brought with him fresh ideas and Jim Gavin spoke after Dublin's victory over DCU in the O'Byrne Cup about how his new charges would have to adapt to "a new style of defending".
There will, it seems, be a greater emphasis on man-to-man marking, and Brennan -- like his defensive colleagues -- will have to evolve.
Not just that though. Brennan has spent almost as much of this early part of the year at full-back as he has in his native habitat of centre-back and while it's probably pushing it a bit to say he sees a long-term future there, he does, at least, acknowledge the importance of versatility.
"I wouldn't be used to playing full-back," he admitted. "But it's important to be able to slip into any position on the pitch. I have enjoyed the couple of games I have had there. It's a new challenge as well. It's a different way of playing.
"You have got to be a bit tighter and you can't be going up the pitch as many times. But I've enjoyed it. It's a different experience."
Similarly, he isn't "too bothered" about the introduction of GPS systems to track players' movement, simultaneously noting "it doesn't help you kick the ball straight or make a block", and "at the upper end of any sport, there is very little between success and failure. It's about getting those inches."
And while Dublin might be less than two weeks away from their first league match under new management, he's not inclined to attach any extra significance to selection against Cork on February 2.
"Sometimes with familiarity, you can take it for granted that the manager knows you are going to be fit come the championship," he explained. "But any time I have played for Dublin, I have tried my best and was looking to perform at my best level and tried to do my best for the team.
"I wouldn't be getting too caught up in that. Every training session and every game, I certainly go out to win and if the manager thinks I'm doing the job for the team, I'm happy."