The Blues boosted their Champions League pursuit with an impressive victory against the champions. Lavia was at the thick of things after starting in the centre of the park alongside Enzo Fernandez.
Speaking after the game, Maresca said that the west London giants are a better team with Romeo in the XI and highlighted that he is so important.
He said: "You can see that we are a better team with Romeo, Unfortunately he has been injured for most of the season. Romeo is so important for the team."
Chelsea have moved to fifth in the league standings after the victory over the Reds. They have a three-point lead and a better goal difference over Nottingham Forest, who have a game in hand.
The Blues have control over their own destiny, considering they still have to face Newcastle United and Forest, who are direct contenders for the Champions League positions for next season.