Why is there so much focus on ”replacement yards?”
Just because a backup may or may not replace all or part of the yards gained or stopped by last year’s starter doesn’t make it an automatic trade-off.
Starters and replacements (and their blockers or sack-producers) aren’t necessarily equal. New guys don’t automatically equal, exceed or fall short of the dude they replace.
So, while scoping out the trade-offs of last year’s guys and this year’s is a fun activity, I’m not sure I’d want to hang my hat on it as an accurate predictor.