The Scotland winger has been battling with a hamstring complaint and was again missing for the 3-1 Scottish Premier League win over Inverness on Saturday.
Nick Ross gave Caley the lead but goals from Kris Commons, debutant Rami Gershon and Miku saw an easy win for the visitors who, in making nine changes to the side that beat Raith Rovers in the Scottish Cup last week, rested most of their big guns with the visit of the Italians in mind.
Lennon appeared unimpressed when told that Rangers have reportedly offered Juventus their Murray Park training ground ahead of the tie.
He said: "Have they? I wasn't aware of that. I have no comment to make on Rangers, they can do what they like."
However, the Celtic boss, who revealed that Commons was taken off at the interval to keep him fresh for midweek, was upbeat about Forrest.
"Forrest is fine," he said. "He has had the two scans and he came through all clear so he will be in the squad."
Lennon was also pleased to see keeper Fraser Forster back in goal after recovering from a neck injury.
The former Hoops skipper said: "He is a wee but rusty but it was very important that he got game time.
"He is fine, there is no reaction to his injury and he will be ready for Tuesday."
The Northern Irishman is more uncertain about Georgios Samaras and Emilio Izaguirre who are battling to recover from their respective hamstring and knee problems.
He said: "They are rehabilitating very well.
"I think Emilio will be fine, now we are waiting on Sami and we won't know, maybe until Monday."