Squad rotation problem. Help!

Hi all, I am manager of a team competing in BPL, FA cup and UCL currently. Due to the hectic match schedule and to keep my players happy, I have to squad-rotate rather frequently. However, there is a glaring problem with regards to squad rotation. For example, when I replace player A with Player B in a new game, Player B tend to almost certainly flop big-time in the match and cost me matches. This seems to happen all the time! This is a frustrating problem, and I have dropped many points because of it. These happens even when the player newly selected to the team has superb morale, no pressing personal concerns and is happy with me. Hence, i would like to ask if is there any way which I can ensure that squad rotation does not result in players underperforming? Is it because of team-talks, in the sense that i have to say something specifically different to him pre-match? Any advice and help with regards to this matter would be very much appreciated!

do you change the individual instructions for the position that you changed players to suit the player coming into the team?

No, i do not. Newly-introduced players had no problems with my tactics previously, but always underperform when they are newly introduced and rotated into the starting lineup. And it is ALWAYS specifically the players who are newly rotated to the lineup who underperform.

As a llama, I rotate my squad quite a bit (out of necessity). I actually find it useful to identify the occasional diamond-in-the-rough whose value is not otherwise obvious. But the short answer to your question is that there's no way to "ensure" that a rotation player performs adequately. The long answer is that you can improve the odds by never rotating a player in unless he's fit, possesses high morale and has been a squad member for a while. The individual team talk can also make quite a difference. Review each player's reactions after each game and adjust your individual talks as appropriate. I tend to try to reduce their nervousness if they're not frequent substitutes. It may also be that the players you're rotating in do not fit into your tactic as well as your starters.