Tuesday's Group H clash at Celtic Park represents the first game that Barca will be without talisman Messi since he hobbled out of the 2-0 victory away to Almeria on Saturday with a hamstring problem that will sideline him for between two and three weeks.
Messi has scored 62 goals in 80 Champions League appearances and netted a hat-trick in the 4-0 win over Ajax on matchday one earlier in the month.
Fabregas, though, is confident Barca can cope without the 26-year-old superstar and has backed himself and the likes of Neymar to come to the fore against Scottish champions Celtic, who recorded a memorable 2-1 win over the Spanish giants in the group stages of last season's competition.
"Messi is the best player in the world, he makes a difference, but he won't play (against Celtic). We can't do anything about that," said the former Arsenal midfielder.
"Without Messi, we will all have to take more responsibility. We have to step up, don't feel his absence and play football without him.
"I might have more offensive responsibilities. I will try and help the team as a striker or whatever other position I play.
"Now I feel confident, in good shape and the manager trusts me. I am in a good moment. Maybe I need to be more consistent."
On Neymar, who has scored three goals in nine appearances in all competitions since joining Barca from Santos in May, Fabregas added: "We need him (against Celtic) and I think he's ready.
"Mentally he's very strong, pressure doesn't seem to affect him, he has clear ideas.
"Neymar is a star in the making, he'll be important in football, everything is in his hands. He can be one of the greatest."
Fabregas came off the bench in Barca's 2-1 humbling at Celtic last November, with the 26-year-old Spain international keen to ensure history does not repeat itself two seasons running as a hostile atmosphere awaits the Liga champions.
He said: "We've learned our lesson from last year.
"They had two chances and scored two goals. It could be a very similar game to last year, especially as it was successful for them.
"We are not upset about last year, we played a good game but must not give the ball away, maximise our chances and score goals.
"If you follow the Champions League you know coming to Celtic Park will always be a tough game.
"I played here with Arsenal as well and it is difficult. They (the Celtic fans) are always behind their team. They take a corner and it feels like a goal."
