I have a question about the football mantra that winning the time of possession battle tires out the other team's defence. Why should they be any more tired out than the offence they have been facing? After all that offence has played just as much and should have the same fatigue factor accordingly, shouldn't it? The only reason I can think of is it must be more physically challenging to play defence. I was wondering if anyone else has any input?
Don't know, but I do know that if your offense is on the field, you're moving the ball and getting first downs, which usually results in points.
The ticats drastically beat Winnipeg in First Downs and Time of Possession.
Its simple, resisting a push is much more taxing then pushing. The art of run and chase. I know where we're going and you dont, bet you tire before I do. 
I think I agree but I thing TOP generally has more to do with the fact that when you keep the ball, you’re scoring and using the clock.
Of course scoring is the reward, but as in yesterdays game the TiCats didnt score much (on offense) in the second half but still managed better TOP, sometimes clock management is better then scoring. Its practised on both sides of the ball too, the D will let the other team’s O march and allow them to use the clock when holding a lead.
Here`s my guess.
I think its because the heavier players tire out sooner than lighter players (If theyre both on the field for a long time).
This way the running backs get an advantage over the much heavier D-Line guys as the game goes on, and therefore running plays should start becoming more successful. This means that the middle level of the defense has to work harder on defending the run as well as the pass, which helps make the passing game more successful too.
Cant wait for Sunday (Its been too long!)
Thanks to everyone who responded, especially those who gave their input regarding why defences tire out more than offences, even though they play the same amount of time. Some pretty interesting ideas.
One thing that has changed in the past couple of decades is the amount of switching in and out that players do for different situations. e.g. receiver runs on, RB runs out. And it seems to happen a lot more on offence than defence. You don't see the DBs and LBs subbing in and out too often.
With every run to the sidelines equalling, say, 30 to 70 yards, shouldnt that mean the offensive skill players get that much more tired by the end of the game? Or maybe sitting out a play or two is more than enough compensation for the extra exertion.
They are also the players that bring the plays in from the bench.