Ospreys battle with injuries
The former Chiefs scrumhalf suffered foot ligament damage in the Bath pre-season game.
He is currently undergoing intensive rehabilitation and is set to return in a month.
Apart from Leonard, five other players are also suffering from injuries.
Dmitri Arhip suffered a setback on his return to playing and is currently undergoing further rehab on his right shoulder.
Sam Davies returned from Wales’ tour with a groin problem and will return to full training this week with a view to being available selection against Zebre.
Hanno Dirksen (knee injury) and Dafydd Howells (shoulder surgery) are expected to return in October, respectively.
Meanwhile, Luke Price also sustained a foot ligament injury against Bath and faces an anticipated six to eight-week lay-off.