Injuries have a multitude of effects though. Not only are key decision making positions effected, but they effect structure and familiarity, even moving Gopps from 12 to 10 has a negative effect. If the side that played Sale had played for a few weeks in a row together, we'd have seen a better team.
On top of that, when you're missing so many key players, it's not just on the match day it's felt, none of our teams are able to train against Jack Willis, Joe Launch, Odogwu, Fekitoa, Mills etc.
Who exactly do you think our centre pairing are training against during the week? It's never going to be able to replicate a regular prem starting centre pairing, because they're simply not good enough (yet, in the case of the youngsters). If all week you prepare against a much weaker side, you're not going to be as sharp as you would be as if you'd been training against better players.
Remove 17 players from the squad for training, and you're really struggling to even put out a correctly positioned 15 to work against.
Then as pointed out, there's rotation. We simply cannot rotate at the moment, which opens up to more niggles and potential injuries. Normally you can tweak one or two players in and out, still ahve them to train against, and be able to more easily integrate the changes into a side.
We were doing fairly well at first, I suspect because whilst we were missing key players, the team had time to train together, get familiar, build patterns and understanding. Then as you lose more players, that cohesion starts dropping (and the niggles etc).