I noticed that sometimes if I make a replacement during the game that changes the formation, it results in very big change in the possession. Recently I had a match where my DC was injured, and I replaced him with DMC. The possession level changed from 60 in my favor to 80 in opponent's, and before I managed to replace DMC by another DC, which restored my advantage, he already scored.
However, an injured player does not seem to have any significant impact. In another game, two of opponent's players were injured, with no replacements, and the possession stayed pretty much the same.
I'd think, the impact of these two events should be the other way around. So I wonder, is this by design?