Willie Carlin and Colin Addison are both in my top 20 Blades. Perhaps a personal affectation, because they were part of my formative years as a Blade.
Little Willie was much more than a 'terrier'. He had good control and vision. In modern terminology, he was technically good. He could pass the ball and got the odd goal, memorably scoring a header [he was a midget, for those who don't remember] in a 2-1 win against some team or other [I know you will fill in the detail

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As for Addison - I remember him as a class act. We hadn't really got into 4-4-2 and all that bollocks at this time. I don't think he was a replacement for Mick Jones at all; he was much more of an old fashioned inside-forward. I remember Mick Hill as the immediate [and vastly inferior] replacement for Jones. What clinches the matter in Addo's favour is this: The Kop [at a time when it generated both volume and wit] had not one but two songs for him [or was it even three - I've a feeling I've forgotten one]! Anyway, altogether now - "Here's to you Colin Addison...."