Think of it another way, say it's £5m he's giving up. Is the next 5-8 years of his career worth more than that. If he rots for another year and continues to regress as he seems to be, he'll worth nothing to anybody.
He might make £5m if he stays, if he does that's likely the end of his career. If he gambles, he might make £2m else where, and then £3-£4m for the season's following. Thus being long term better off, not to mention actually playing.
He's got plenty of till, for me, he'd be better off gambling and backing himself. I personally think he's good enough to relaunch his career, if he stays I fear he'll never get that chance.
I hope he backs himself, at 31(?) football should still mean more to him.