What to do with underperform player?

[b3ast]

IMO yes,sell him.If he's young and high value you can easily buy older 5* player who will play much better than this one.If he's old,well it's time to buy someone to replace him

Regarding that 2* DC - keep him until you can bring in better player.Then you can either keep him as reserve or release him

PS: I've noticed that you're comparing DMC with DC,and if you're playing your DML/DMC in DC role then it's normal that he has bad stats