While concerned with Lavia's fitness, Maresca was pleased the midfielder's form was recognised.
"First of all we are happy for Romeo that he is back in the international squad, that is the first thing we have to think," said Maresca.
"If for any reasons he was not getting minutes, it is not a problem if Romeo keeps doing the right things and he is there the next time.
"The important thing for him and for us is that Romeo is back to his level and back with the international team."
Maresca also said: "The reason why he is not available for the Conference League squad is because we want to take care of him – players like Romeo and Wesley Fofana and those players who were injured last year.
"But Romeo is very young, he is 20 and he has to work hard. His career is going to have more injuries because it is part of being a player and it is normal.
"But in this moment, he is good, he is fit, he is back and he is doing well. He has to continue to work hard."