Yeah there's about 10 plays a game that determine the outcome usually. If you can have fresh guys pursuing a running QB on two of them, probably win that one. If Schoen catches the ball, if Oliviera doesn't fumble, if no pick six. Each and every one increases your chance of winning, right?
The point is when you have McCrae mostly standing on the sidelines (or bobbling punts), Jackson mostly standing on the sidelines and you could potentially actually have an impactful player out on the field for those big plays, or have your Jefferson/Jeffcoats out there at 80% energy instead of 40%, you've increased your chances of making one of the plays to win the game. The chances of the guys doing their job and executing increases when you have better players on the field as close to full capability as possible in a football game.
If you make the choice to have more or less dead spots on your roster with a shallow DL but the luxury of having a couple Americans with very little role on O on top of an American kicker (obviously needed but has consequences through the roster), you've handicapped yourself and made the margin to victory thinner.