One of the biggest differences is the size, athleticism, and talent of opposing Ts and OL in general. Back in those days, even back not that long ago, OL were canadian ham n egger types. Now we have guys like Tyler Elsbury. He's faster than a handful of our skill position players, 6'6 and 333lbs. Our 2nd-best T (imo) is Hunter, who is 6'8 330 jumps a 30" vert, can put up 30 reps, and jumps almost 9 feet broad. The average DL is getting smaller in the CFL. We see far more 235- 249 lb DEs, and a lot more tweeners 275 and under who play DT and edge. Even if you are a bigger DE, say 265-270 and not playing inside, you are giving up an insane amount of weight to the T every single snap. Playing inside is even rougher, as you are likely to be hit by multiple OL. DL has gotten more athletic as well, but premium big athletes seldom go to DT over OT these days. OT is a vacuum at all levels, sucking up the best and biggest players teams can find. The gap, though, has gone from a size vs. athleticism battle on the edge to DL having to punch up in weight. The evolution of sports training has guys focused much more on explosive quickness and 10-yard splits rather than basic cardio-style run-jump stuff. And those fast-twitch muscles need more rest, and so does the whole athlete who is fighting an uphill battle. A tired DE, might be at 50%. But a rusher under 90% is likely to get his butt whupped unless he is elite. Another harsh reality of life in the CFL is that we don't get the polished players we used to. We seldom see pass rushers come up with more than a raw skill set and maybe 1 decent move anymore. The easiest way to succeed on the DL and create disruption is to cycle through guys quickly and keep them running as hard as they can, subbing them to keep them fresh. The longer your recovery system is in stay-fresh mode and not in heavy recovery mode, the better as well. If you are tired in the first quarter, you will not recover to 100%. You will peak lower, and each time you tire, the cycle will repeat. The OL also has the tremendous advantage of knowing what they will be doing before the snap and being able to dictate the play. Having to react and try to stop what you don't know demands a great deal of athleticism to overcome. As well as other factors, it is a great drain on athleticism. Speed is a butt saver as much as anything on D. Actively subbing high-wear positions is spreading like wildfire across football. It isn't just DL; it's RBs and more sharing the load. OL, WR, and DB are really the outliers in this area. WR and DB are paired in being less physically demanding and being tuned more for marathon-type activity. Ol, is so thin across all levels of football that the drop-off after the 5th guy is far too steep.