Jackson was absent due to injury as Chelsea were knocked out 2-1 in Saturday night's fourth round tie.
Maresca said, "Yeah, sometimes I think you need to play games without players to realise how important they are. We said many times about Nico: he is important on and off the ball. Off the ball, his intensity is very good and on the ball, he is always a threat.
"Overall, even without Nico, the game was both. We started the game very good. In the first-half, probably the only shot on goal they had was the goal. We controlled, we created some chances and the second-half, more or less it happened the same - probably the only shot on goal was the second goal.
"We had a few chances to draw and we missed. Now, if there is something good after a defeat is now we can be focused on the Premier League and Conference."
He added, "As I said yesterday or two days ago, it won't be long but we will see if he will be available for the next game."