Redknapp revealed Lennon's frustrations at not being fully fit in such an important campaign.
He said: "Aaron is low when he is not playing, and is working hard out on the training ground with the fitness coach, is in the medical room getting his treatment, trying to get himself fit.
"Another little setback is not what he wanted, but he will get on with it.
"When he does come back, he will be as good as ever."
Redknapp added: "Obviously we miss him - he has got fantastic pace and scares teams to death with his ability.
"But we have been lucky that David Bentley has come in and shown what a top player he is as well."