Lallana's and Allen's injury record is just as poor. I believe Lovren has missed the same amount of games due to injury as Sakho has over the past 2 years. Point is - we have quite a few injury prone players but some will get more chances than others.
I thin kthe big teams worries are founded in the fact that 6 into 4 doesn't go and 8-20 can all beat a top side on thier day thres so much moeny in the game anyone can beat anyone so teams need to be right on it every game to collect the points.