Tenant Deliemma

[Mineto Anfield]

I was helping a friend who needed a place to stay and rented to him for $550 This being the 4th year I increased the rent to $625, but the increase still leaves me at a small loss each month. Although there was a little pushback on the increase he is paying it. The real issue I have is that since I've contracted with a very good property manager she tells me that I could be getting $1,000 at least. I really want to get the rent that the property will bring.
Any suggestions on the best way to approach the tenant on this needed increase?