Midfielder Enzo Fernandez may return to action after missing a week with a knee issue but Maresca said Chelsea would not rush the Argentina international back as they look for their fourth straight win in all competitions.
"Enzo took part in the session yesterday. We have one more session this afternoon and we will decide with him tomorrow. It is not something we have to be worried about. It's to try and protect Enzo," Maresca told reporters on Tuesday.
Centre-back Benoit Badiashile was the latest Chelsea player to pick up a knock last week, the sixth on the injury list.
"It's difficult, especially because most of the injuries we had were one or two days before the game," Maresca said.
"We're trying to adapt. It's complicated because sometimes you plan for some players to play one week, but then you need that player because of another injury."
No 'punishment' for players over red cards
Chelsea are also facing an issue with player discipline after picking up four red cards in the last six matches.
"For sure, it's something we can do better. Some of the red cards, we can avoid that ... the other side, they do not want to concede and they want to continue to be aggressive," Maresca added.
"Personally, I'm not that kind of manager to punish players ... I have four kids, when they do something wrong, I do not punish them. I try to teach them to do the right things. I try to do this with the players too. This is the way I like to do things."
But Chelsea, who had a three-match Premier League winless streak and lost their first Champions League game to Bayern Munich last month, have bounced back with a scrappy victory over Benfica and back-to-back wins in the English top-flight.
"We were not happy with the result at Bayern, but the performance, we were happy with. We knew that was a difficult game," Maresca said.
"Benfica, we tried to prepare the game to win the game in the best way, but when you face this kind of club there are always things you can learn after the game. It is going to be exactly the same tomorrow.
"It'll be a difficult game. (Ajax) are a club that have won this competition in the past. They want to prove to everyone that they can come here and beat us. We are going to try and do exactly the same."
Chelsea are 18th in the Champions League table with three points from their opening two games, while Ajax are second-bottom without a point after two defeats.