But Toni Rudiger is set to start Wednesday’s clash – and will wear a protective mask after suffering a facial injury in the first leg.
Thomas Tuchel’s confirmed Kovacic is the only injury absentee, with the Chelsea manager’s main dilemma being over who he will play in attack.
Chelsea hold a slender advantage after drawing the away game 1-1, which saw Timo Werner fail to score from point blank range.
Kai Havertz was left out of the game in Madrid – but scored both goals in Saturday’s 2-0 win against Fulham to put him in contention to start.
Tuchel said on Tuesday: “I will wait until tomorrow and make my decisions very late like I usually do.
“I have my ideas in my mind, but I have been too long in the business to know that anything can happen in the last training sessions and I can change my mind.
“I need another sleep and tomorrow I will decide on the line-up. I will give it to my team first this is the way it is. I want to be sure we play a good match with the line-up we have, a strong performance.”
Addressing his attacking options and Werner’s ongoing struggles in front of goal, Tuchel added: “I believe strongly that Timo wants himself to score absolutely this goal (in the first leg). He knows that he had a huge one in Madrid.
“But I think we all have to accept that sometimes strikers misses chances, big chances, and this is part of the game.
“Everybody needs to step up and take responsibility for scoring and for defending, I think we create enough chances, enough touches in the box to maybe score more goals.
“And this will come with time, a bit more experience, adapting and self confidence.
“I’m pretty relaxed about it, and trust my players no matter who starts tomorrow, and like I said we do this as a team.
“Nobody has to do this on their own, we do this together and there are many situations to solve tomorrow, not just thinking about scoring.
“We will try to create chances, to create good intensity, and from there we trust our guys.”
Chelsea predicted XI (3-4-2-1): Mendy; Christensen, Silva, Rudiger; Azpilicueta, Kante, Jorginho, Chilwell; Ziyech, Mount; Havertz.
Squad: Kepa Arrizabalaga, Willy Caballero, Edouard Mendy, Reece James, Cesar Azpilicueta, Antonio Rudiger, Andreas Christensen, Thiago Silva, Kurt Zouma, Ben Chilwell, Marcos Alonso, Emerson, Callum Hudson-Odoi, Hakim Ziyech, Christian Pulisic, N’Golo Kante, Billy Gilmour, Mason Mount, Kai Havertz, Faustino Anjorin, Jorginho, Tammy Abraham, Timo Werner, Olivier Giroud.