Anderson was missing from training yesterday ahead of the clash, with the aggregate score locked at 1-1.
Pereira said in his preview: “Today, he was not able to train.
“He has personal problems and we have to respect. We will see (about tomorrow), we need to wait.”
Forest host Porto knowing a massive relegation clash awaits this weekend against Burnley.
Pereira added: "In this moment, I need to think about both games. It is important to balance the energy and to face Burnley in our best condition because it will be a tough game again.
“Tomorrow, when we are looking at the first XI and the subs, we have to look at the time for everyone on the pitch, and the potential of extra-time. If you go to extra-time, it is another challenge.
“But I am positive. We know the game will be very tough. I know them (Porto) very well. We need to play at a better level than we did in the first leg.”