Ahead of today's clash with Everton at Stamford Bridge, Maresca reflected on the teen's development over the past 12 months.
"The good thing about Josh is that in the moment we give him a chance, he is always doing well," said Maresca.
"This is the reason why I said many times he is going to be a big player for this club. It’s just a matter of being patient, waiting for the right moment and also knowing that if he continues to perform in the way he is doing, he is going to have more and more chances.
"With Trev (Chalobah) and Wes (Fofana) we had four or five games with clean sheets," added Maresca. "Sometimes you are looking for stability.
"But you know when you have a player that you need and he is always ready to perform, it’s so important. Josh has to continue to do what he is doing."