He needs rest. They really need to find a way to rotate him a lot more in the next season, or maybe give him a few additional weeks off after the copa this year, start the season without him. He played an insane number of games, both for his club but also for Argentina, making the final of the World Cup in 2014, the Copa in 2015 and now he has to play again a big tournament this summer. Much more than physically it has to be mentally draining.
I wouldn't be surprised if Enrique actually wanted to rotate him a lot more but he simply refuses to and wants to play as many games as possible. It's a difficult decision to make for the manager, if the player simply doesn't listen.