Renato Veiga, Pedro Neto, Christopher Nkunku and Kiernan Dewsbury-Hall, his first for the club, were the goalscorers for the hosts.
Afterwards, Maresca said: "We are performing not only in attack but defensively very well. We are happy. I need to repeat always the same: For sure, we can do many, many things better - we can attack better and defend better. Tonight probably the most important thing we can learn is even if we are 4-1, even to the final whistle you have to switch on, you cannot switch off.
"I think we conceded the second goal just because we saw the game was already finished. I think if we want to be one step forward, even when you are 4-1 and the game is almost finished, you need to continue and not concede another goal. We are really happy with the performance. We approached it very well. These games are never easy. So I am very happy with the performance and the result."
On his changes for the night, he also stated: "We do not have two teams. It is one team, only one team. The ones that are playing tonight does not mean they cannot play Sunday or the next Premier League game. In this moment it is like this but the important thing is that changing players, you can see the identity of the team.
"The last game against Brighton, tonight, the Barrow game, the West Ham game. This is the most important thing. We continue in the same way. For sure, I can understand in this moment it is like this but in football things can change very quickly.
"The last three or four games, since we started, the identity is clear, the purpose is clear. For sure, 100%, we can do many, many things better. We can attack better. Tonight I think we attacked very well.
"They were a low block and we were trying to find a solution in the last two days to prepare for this game. Defensively we pressed very well, when we lose the ball we tried to recover it immediately. For sure, there are things we can improve like the two goals we conceded; especially the second one. The first one can happen, the second one, we can avoid that."