Sad to say, you have to put them in a real match, especially CL, most good players shine in their first game either scoring or giving assist(s), which is why I watch the simulation. Most people look out for the goal scorer (but the game is programmed to test your insight), but I note not only the scorer, I look at the assist and the player that gave the ball to the assist - that is a key player.
Another way is from the Assistant Manager's report, I think the game is also programmed to report your good players to you. Especially, when someone else other than the MOTM is praised.
Below is the new goalie I bought being praised in his first game, and he wasn't the Man Of The Match:
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https://uploads.tapatalk-cdn.com/202...c4c5e5a37e.jpg