A search doesn't give a result, so given the title, there's one definite bug and one possible depending on your input.
Definite bug, let's see if I can explain:
My team is:
Reina; Fabio Aurelio, Agger, Kyrgiakos, G Johnson; Meireles, Lucas; Babel, Cole, Kuyt; Torres.
I decide to bring in Skrtel for Kirgyakos.
Meireles gets injured before the sub happens. The injury is bad so it needs immediate answer, I'm taken to tactic screen.
What do I find?. Meireles in red, and in the place of the Kirgyakos is not Skrtel or the greek, but it's empty. There is no player there!.
So I curse at it, but notice that Skrtel figures as still in the bench, so I bring him for Meireles and then place him in the spot of the greek guy, then I move Cole from AMC to MCL where Meireles was. I confirm the changes.
The, seeing the form popup, I see Meireles shows as if he was on field. I go to tactics and see the first screenshot: Meireles is nowhere to be found and in his place is Meireles.
Then I do the sub to bring Skrtel in his place, I drag, drop... and see screenshot 2, Kirgyakos pops in the AMC area (as if moving MCL to DCR moved him there and then Cole from AMC to MCL).
After that I undid the sub and Kyrgiakos still showed, so I made a sub of Meireles for Maxi Rodríguez, placed Kyrgiakos back to DCR. I can't tell what was the result of this because when I noticed this the match was in its last thirty seconds and so the match ended before the sub could be performed.
Something like this seemed to happen in a set pieces creator, when in one of the throw ins one of players had no icon showing on the screen. I would bet it originates from the sme piece of code.
The possible bug:
Too easy to get bad injuries?. In two consecutive matches (played six or seven) I got a player injured for two or three months. It can be bad luck, but I leave it in case too many of you have found this bad case of injuries.