Diego Costa's move to rejoin Atletico from Chelsea was completed on the eve of the Group C contest, with the striker able to play once the Spanish side's transfer embargo is lifted in January.
Costa scored only two goals in 15 Champions League games for Chelsea, while Hazard has five in 37 and is yet to start in the Premier League this season due to the broken ankle sustained in June.
But Chelsea head coach Antonio Conte says Hazard is now fit to start and that the Belgium playmaker can go up a level now the Blues are back among Europe's elite.
Conte said: "Last season, he showed in every game great talent, to be a really good player, a top player.
"This competition is very important for him, but I think it's important for the team.
"This competition brings you to another level
I think he has all the possibilities to do this
It's the right moment."
Costa returned "home" after claim, counter claim and an acrimonious end to his three-year Chelsea spell which featured two Premier League titles and 59 goals in 120 appearances.
The initial loan deal, which will become permanent for a fee of around Â£58million at the end of the season, was announced ahead of Atletico's first European match at their new Estadio Wanda Metropolitano home.
Costa said on Atletico's website: "I'm very happy to return home, I've always said it, Atletico is my home, I'm very, very happy."
Morata is Costa's direct replacement and has started his Chelsea career with six goals in six Premier League games, including a hat-trick last Saturday at Stoke.
Morata was in and out of the team at previous clubs Real Madrid and Juventus, but is integral to Conte's Chelsea.
The Italian said: "For the first time, he's having a great chance to start as a number nine, to have the responsibility, the right pressure, and he's responding very well to this pressure.
"To start in this way you must be very strong."
Chelsea were absent from the Champions League group stages for the first time since 2003-04 last season.
And Conte wants to measure his team against one with European pedigree in Diego Simeone's Atletico.
Conte added: "For us, it's very important to play this type of game: away against one of the best teams in the Champions League.
"I think it's the right moment also to understand where we are."
Source : PA