Maresca told Sky Sports: "We scored the first one and could have scored the second goal two or three times. The game would have completely changed. We missed.
"The team was there but in the last minutes we conceded for 1-1. The second goal changed the game. Robert is the first one [to admit] he knows he has to do better. Working hard every day [is the way to improve]. We try to have conversations with all of them.
"We are making progress. We are better than one or two months ago. These moments will make us better."
He added, in his press conference: "Robert, for sure, is completely aware he has to do better. He knows perfectly. In this moment it is like this. The good thing is he is the first one knowing, aware that he has to do better... We trust Robert for sure. He is completely aware he is making mistakes in this moment. We trust Robert. We have one entire week and we will see the reaction for the next game."