Mauricio Pochettino has confirmed Christopher Nkunku has not suffered a serious injury but will miss Tuesday's "really important" Carabao Cup semi-final second-leg clash against Middlesbrough.
The Blues face arguably their biggest game of the season so far, looking to reach the Carabao Cup final after losing the first leg 1-0 at the Riverside Stadium two weeks ago.
Chelsea will be without 10 first-team players on Tuesday but will still be expected to beat a Boro side sitting 11th in the Championship.
Nkunku, who saw injury delay his debut until December, had hoped to shake off a hip injury to be available but will be again watching from the sidelines. Pochettino told reporters: "No, [Nkunku] is not available for tomorrow.
"It is a shame but he is still recovering from some suffering in his hip and we hope he can be back as soon as possible with the team - it's not a big issue."
He added: "Malo Gusto is out tomorrow. He suffered an injury against Fulham and is not available for tomorrow."
Chelsea have recalled midfielder Cesare Casadei from Leicester City and winger Diego Moreira from Lyon. Casadei is cup-tied for both the Carabao Cup and FA Cup but Moreira is available.
"We need to assess them both now after they came back from their loan," Pochettino explained.
"They have good potential and they are going to be part of our squad and we will make the decision whether they will be part of the squad or team every week. It is good news because we suffer a lot of injuries so it is good for us."
A win over Middlesbrough could ease pressure on Pochettino and his young squad by setting up a cup final against either Liverpool or Fulham at Wembley Stadium in February.
Pochettino said of the game: "It is true, we cannot lie, this is a passport to go to the final to go to Wembley. It is a really important game for us.
"It's really important for us, the club, for everyone who wants to be in the final. First of all, we need to beat a very good team that is Middlesbrough after a first leg that beat us.
"Of course, it will be tough after the first half but we are confident we will have a very good game in front of our fans at Stamford Bridge and take advantage of the energy from our fans. It's a massive chance for us to go to a final and fight for a title."
