That came out wrong, I don't blame Oscar, because he's playing out of position, just saying that it was his job to cover for Luiz. As for Iva, he made a lot of mistakes in the first half, this was not one of them. He was doing his job in this scenario which is to go and press the player with the ball so he can't pick out the best pass. However, Oscar who was trying to get back in Luiz's place realized that he won't be able to make it and changed his run midway to press the player with ball. Iva then had to sprint back to cover back where Oscar, as the DM, was supposed to be, but by then he was too late.