The 33-year-old has struggled for game time in recent weeks amid growing reports linking him with a move away from the Greens.
The former Chelsea ace endured a frustrating injury spell since his move to the Greek giants.
He came out of blocks, impressing in games after initially bogged down by persistent injuries.
But manager Andrea Stramaccioni has opted against fielding the Ghana international despite being fit.
The former AC Milan man says he's surprised at his lack of playing time at the club.
“As far as I know is not the case for technical reasons, or has to do with injury problems. I am healthy and I train every day since last October when my injury was going better," he told gazzetta.gr
“There is no concern for injuries to my discussions with the coaching staff. Not due to technical reasons or any problem related to football.
“It must be something else, but I guess that is something that must be answered by someone else. As for me, I am always ready to fight, but I do not have this possibility in recent months.”