Shepherd spent £15million on signing the England hitman from Spanish giants Real Madrid two years ago.
Owen has made just 13 starts for Newcastle.
Shepherd said: “Michael owes Newcastle a lot, I’ll put it as bluntly as that.
“I think he’s played more times for England than he has for Newcastle — so I think he owes the fans quite a lot.”
Shepherd has also revealed that Owen’s £9.5m buy-out clause at Newcastle ends tomorrow.
He added: “Without it, I don’t think we would have done the deal but it is only valid until July 31.
“After that he would have to stay for another year — unless it was in the club’s interests to let him go.”
