He is 100% premiership quality. Cliche but true... form is temporary and class is permanent. Even allowing for injury he's not been afforded the opportunities over the past year or so.
If he can put a good season in he'll be back in the premiership in absolutely no time whatsoever.
"Form is temporary, class is permanent" doesn't really apply to your average club player. He wasn't at the same level as guys like Robshaw, Brown, Care, etc