From my experiences since I started playing this game, there have been a very rare case where a player performed better when put at another position other than where he is expected to do well according to what information is provided to you visually (attributes, special ability and so on). Way back (around 2 years ago), I had an MC/AMC with shadow striker special ability that was bought from the auction market. He did not perform as expected at AMC position and nothing much at MC position too. I quit playing the game seriously at that time, and I was no longer maintaining my team as such. In some matches, the game put him as DMC when the first team DMC got injured. He had very good ratings, and even better than the DMCs I had in the team. For that particular case, maybe the player was an MC and was trained AMC and the shadow striker special ability, but he turned out to be playing better at DMC position despite being marked out of position.
Then there is another situation: the information provided concerning the player indicates that the player can do well at another position. I had a few players like those. I trained some them that particular position and some of them did well but there were under-performers or players that did not perform as expected too.
But in this game, for certain occasions and even periods, even the players that should not be performing well when put to play at certain positions will unexpectedly do well probably because the game wants that particular team to do well for that occasion or during that period. This includes the fixed matches and the troll matches.