The duo left for Paris Saint-Germain in July 2012, but the 25-year-old warned his team-mates that the the likes of his former Arsenal team-mate Mathieu Flamini put up a fight in their Champions League clash on Wednesday.
"Well, obviously when you lose two key player likes Ibrahimovic and Thiago Silva there’s obviously a lack of quality in the squad," he told the Blaugrana’s official website.
"But that means that other players have to step up, but like Mathieu in that case, he’s back to full fitness he’s doing very well, he’s doing what the coach is asking him to do, and for me it’s amazing to see him play and do what he’s doing because he deserves it.
"I think the games against Milan are always difficult. Last year we also played in the quarter-finals against them, and it’s one of those exciting games.
"It’s one of those games you never need to be motivated because your mind and your body ... you know straight away that it’s a really important game and you need to be at your best if you want to go through.
"So it’s one of those games that a football player really likes to play, and hopefully we can go through."I think the tie against Milan will be very exciting and difficult. They have a great history in the Champions League, great players, great fans, and it will be a very difficult one.
"But we just have to focus that it will be a very important game and we need to be at our best if we want to go through."
Fabregas went on to say that he has memories of the Gunners' 2008 victory over Milan at San Siro, and is looking forward to playing there once more.
"Well I think San Siro is one of the most amazing stadiums I've ever played in," the 25-year-old continued. "Obviously I have great memories of when I was I at Arsenal, of what we did there, which was amazing.
"But obviously it's one of those stadiums that you step in there and you think: 'Wow, it is going to be an exciting game', and you feel it’s the Champions League, you feel you want to be there playing.
"And obviously, once you get in that stadium, you have to mean business if you really want to win."