There are aspects to his game that are really good, namely his shot stopping when one on one and his reactions.
But there are aspects to his game that are really substandard, namely his decision making, distribution, propensity to punch when he should and could catch, his weakness down to his left hand side and his positioning behind a wall for a free kick.
Also he nearly 30 and should have been addressing those weaknesses. We may not find a replacement who is as good at stopping shots that aren't low down to their left but I'm sure we can find someone who is solid all round.