Mertesacker has been a superb signing.

If the best you can come up with is a lame joke and critique that he is "not perfect", other than admit you were wrong, the best thing you could do would be to shut up about him. For now at least.

Of course, with the season being long, no doubt at some point Merts will make a mistake with him not being perfect and all. Why not wait before posting so you can declare yourself right?.