The winger was left out of the side that beat Inverness Caledonian Thistle 3-1 in the Scottish Premier League yesterday due to a hamstring injury.
Manager Neil Lennon told Sky Sports News: "Forrest is fine. He has had the two scans and he came through all clear so he will be in the squad.
"[Fraser Forster] is a wee but rusty but it was very important that he got game time. He is fine, there is no reaction to his [neck] injury and he will be ready for Tuesday."
The Italian side face the Scottish champions in the first leg of their last-16 tie at Celtic Park on Tuesday evening.