Right-back Malo Gusto put the hosts ahead with a header in the 51st minute, but the game was still in the balance when the 18-year-old was introduced just after the hour-mark.
Estevao, who has largely been limited to substitute appearances in the Premier League, gave Chelsea a cushion just one minute after coming on, setting up fellow Brazilian Joao Pedro for their second goal.
"I was very worried before this game. These are the worst games, they're tricky. Everyone is thinking it's going to be easy," Maresca told reporters.
"I can understand first half people were not happy because we didn't score. Then when Estevao came on the energy raised because people love that kind of player.
"You can see his talent. We are trying to help him to adapt and give him the right minutes. He arrived from Brazil, he needs time to adapt, but he's going to start games for us in the future."
Maresca also hailed winger Alejandro Garnacho's work rate after the Argentine international, signed from Manchester United in August for a deal reportedly worth 40 million pounds ($53.68 million), bagged two assists.
"He arrived from a club where he was not training 100% so his physical condition was not good," Maresca said.
"Slowly now he is better. He knows that to play with us he needs to be good on the ball and off the ball otherwise he's not going to play. We are very happy with him."
The 3-0 win provisionally moved Chelsea up to second in the standings, a point above Manchester City who have a game in hand and play Liverpool later on Sunday.
The London club next travel to face Burnley in a league match on November 22, after the international break.