Celtic saw their domestic silverware dominance end at Celtic Park courtesy of a 2-0 defeat to Ross County, who scored a goal in either half to pull off a big shock.
Under pressure boss Lennon brought on four substitutes during the course of the cup tie, but Celtic could not turn the game around and slipped out of the Scottish League Cup.
McManus feels the Celtic players are going through the motions and not having to suffer the consequences due to no fans being in the ground.
And the former Hibernian attacker does not see how Lennon can remain in his post as Celtic manager.
“Can’t see how Neil Lennon can possibly survive this result and performance”, McManus wrote on Twitter.
“Awful again in both boxes.
“Players going through the motions and getting away with it because no punters in the stadium.”
Celtic have won just twice in their last ten games across all competitions and it remains to be seen how much longer Lennon can keep hold of his job in charge of the Scottish champions.