Manchester United manager Jose Mourinho says it will be mission impossible for Saint-Etienne to overturn their 3-0 first leg loss against the Red Devils ahead of the reverse fixture on Wednesday in France.
A Zlatan Ibrahimovic hat-trick at Old Trafford sealed a comfortable first leg advantage for Mourinho's side last Thursday.
Speaking in Tuesday's pre-match press conference, Mourinho however warned his team that they can't afford to relax.
"No (on whether United have already qualified for the round of 16) because we have not already done the job," Mourinho said.
"It is not already done. Their manager motiveates his players very well and thanks to the support, with the help of the fans.
"Three-zero is indeed a very good result but if we play normally, as we usually play, I think it is mission impossible for Saint-Etienne.
"Even though I think we played badly in the first 45 minutes of the first leg. I shall tell my players to forget about the final on Sunday. I want my players to be focused."
Mourinho stated he expects a charged up atmosphere from Saint-Etienne fans.
He added: "I played here with Porto and I came later for Saint-Etienne versus Lyon, as I was getting Lyon in the Champions League draw. I know the stadium, it is more beautiful now. I know the atmosphere. I know tomorrow it will be amazing to play. Everyone likes that."
On the availability of skipper Wayne Rooney for the clash against Saint-Etienne and in Sunday's EFL Cup final against Southampton, Mourinho said: "I don't know (on Rooney). This morning was the first time he trained and didn't even train 100 per cent with the group. You saw 15 mins open to the press and yes, he was doing the warming up and the basic things after warming up but then when the training session was higher in intensity he was not training. No chance for tomorrow, he is not here, he stayed back training, and let's see for the weekend."
Mourinho added regarding Rooney's future: "If one day Rooney wants to leave the club then it isn't because of me, I'll never force a legend out. You have to ask him."
And commenting on Luke Shaw's continued bench role at United, Mourinho said: "He (Shaw) stayed behind in Manchester because I am playing with Daley Blind, Marcos Rojo, Matteo Darmian, and all of them are playing the way I like a full-back to play. Luke has to wait for his chance, he has to work better and better, knowing that I give nothing for free. When I give something for the players it is expensive for me, it is not cheap. They have to work really hard every day, they have to play well, so he has to wait and in this moment he is behind the others."
"Potentially he has many things that I like, but one thing is potentially and another thing is on the pitch to express all the qualities I like a player to express. He has to keep working like Mkhitaryan did for a long time."