Kenny Miller scored 3 goals in 1193 minutes in the league last season, a goal every 400 minutes.
Moussa scored 5 goals in 1693 minutes, a goal every 330 minutes.
Leith-Smith got 6 goals in 1430 minutes, a goal every 240 minutes.
He's following the exact lines strikers do as they get older. His output is regressing and he's playing further off the front. He contributed no assists last season, while having a worse goal record than two strikers most of your fans despise, despite him playing in a far more dominant side.