David Luiz, 25, picked up his injury during the FA Cup semi-final clash with Tottenham and has missed the crucial ties with Barcelona.
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However, with John Terry suspended for the final, Luiz"s return is now more crucial than ever.
"They’re progressing well with their injuries. But it’s impossible for me to give you a date for their comeback now. Hopefully, they’ll be ready before the Champions League final," Di Matteo told reporters.
Asked whether either David Luiz or fellow centre-back Gary Cahill would be fit enough to play a part in next week"s FA Cup final, Di Matteo was unsure.
"We need to check their progress on a daily basis. For the Newcastle game [Wednesday], it’s too early. We will see on Thursday and Friday.
"We have tried to give the players as much recovery mentally and physically as possible. It’s very challenging, very demanding. We are doing our best to keep them as fresh as possible, to put out a team that has enough energy to win the game."
