"I'd have thought that next year will probably be my last year," he told The Daily Telegraph. "I have one year left on my contract but this year hasn't been great and whether it will get any better next year, I don't know.
"I've had a knee injury this season. I seem to get a three-month knee injury every season now.
"It sets you back and I haven't contributed as much as I would have liked to have done. I get pain my knees most days and I definitely feel my age.
"The eye problem is still there but I have become totally used to it now and that's not an issue.
"But I've dipped in and out of the team this season and really struggled, to be honest, playing one game every 10 days.
"Some people adapt to that and some enjoy it but I don't think it has worked for me.
"It's hard to keep yourself fit when you don't play every week."