Despite receiving additional rest, Fernandez wasn't deemed fit enough to earn a place on the bench in the East Midlands. Speaking on Tuesday afternoon, Maresca emphasised he'll continue to safeguard the Argentine but he has a chance of returning against Ajax.
The Blues boss said: "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.
"It's difficult, especially because most of the injuries we had were one or two days before the game. We are 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."
Maresca also delivered an update on Liam Delap, who's been managing a hamstring injury.
The 22-year-old striker sustained the problem during Chelsea's 2-0 victory over Fulham just before the September international break. Thankfully, Delap avoided the need for surgery and will be back in training sooner rather than later.
Maresca revealed: "Liam is very close. He is not working with us yet. He is still out. Hopefully, in the next days, he can start training with us."
With Delap remaining sidelined, Marc Guiu will be eager to establish his credentials for a starting berth.
The 19-year-old forward has barely featured since Chelsea brought him back from his loan spell at Sunderland.
Nevertheless, he made an excellent impact when introduced at the interval at the weekend.
Regarding Guiu, Maresca added: "We have him and Tyrique [George]. He can play as a number nine.
"We have different options - we will see after the session this afternoon," the Chelsea manager continued.
"We trust Marc. We trust him last year, he was playing in the Conference League. We gave him some Premier League games. He will play games for us, for sure."
Chelsea will face Ajax at Stamford Bridge on Wednesday evening.
Speaking about the Dutch powerhouses, Maresca stated: "They always try to play their football. For sure, it will be a difficult game.
"They 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.
"It's a nice competition because you play against a fantastic club. We were not happy with the result at Bayern but the performance, we were happy with.
"We knew that was a difficult game. 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."