Chelsea defender Antonio Rudiger is expected to miss the rest of the season after picking up an injury in the 1-1 draw at Old Trafford on Sunday.
David Luiz has backed Andreas Christensen to step up in Rudiger’s absence.
Christensen was a regular starter for Chelsea last season under Antonio Conte until he made an error which cost Chelsea in the Champions League against Barcelona last season.
Luiz insists Christensen has put the Barcelona nightmare behind him.
Luiz told Standard Sport: “Andreas is a great player, a great boy. I like the way he thinks about football and looks to play the game.
“People always seem to want to remember what they want to remember, we can’t do anything about that.
“What happened to Andreas against Barcelona is in the past and people shouldn’t talk about it. It is not nice to talk about it. Chelsea lost against Barcelona, it wasn’t Andreas losing against Barcelona.
“Have I tried to help him since what happened last year? Yes. He is a great friend and he listens a lot. We always help each other.
“He has a lot of quality when he has the ball at his feet on the pitch. He is good at reading the game, he is an intelligent and clever defender.”
Luiz also revealed he has been talking with former Chelsea forward Salomon Kalou, who is now with Hertha Berlin, to get tips on Thursday’s Europa League opponents Eintracht Frankfurt and their striker Luka Jovic, who has scored 25 goals for the German side this season.
Hertha Berlin played a goalless draw with Frankfurt over the weekend.
Luiz added: “I have spoken to Salomon about how they play. They had a game against them the other day and drew 0-0 against them. But I can’t tell you what he told me!
“But I have watched Jovic ahead of the tie. He is doing an amazing season and is a great striker. When forwards are confident like he is right now it is even more difficult. His confidence is so high because he has been working for that.
“Eintracht have a fantastic team, they like to play three at the back. They play with a lot of physicality but also great players with technique. It is going to be a tough game for us.
“But I am looking forward to this semi-final. I work hard every day to be on the pitch for games like this and try to do my best.”