The drama between Del Potro and DC Captain Martin Jaite is a replay of the drama between Nalbandian and former DC Captain Tito Vazquez. It's the same story with different cast members.
I think Gabriela Sabatini should take over as Argentina's DC captain. She could take care of these guys. If Nalbandian acts out, Sabatini will punch his face and starve him for a week. If Del Potro acts out, she'll give him a death stare to put him in his place. She would then give hairstyling tips to Charly Berlocq, after which she will sub in for him in doubles to win the trophy for Argentina