Big squads get injured more.. I always suspected it but getting more sure about it every season as its my 3rd season with 15 to 17 players, and I'm gettin very little injuries again.. I used to have full squads (22 players) and very often had 5 or 6 guys injured, not anymore..
Hope that helps

Ps: u ll be using more green packs to compete in CL and cup since you have less players, but then u use almost no red packs..