Walker has been, and still is, an immense defender. Fast, aggressive and never lets us down. I think he's been a great signing for us.
However, he isn't getting any younger and there's 3 things about him that makes me wonder if he will leave:
1) He's only got a couple of years of blistering pace left. Has he got the nouse to stop attacks when his pace declines? I'm not entirely sure.
2) His off the field antics. Not much else to add to this, but you know that Pep won't be impressed.
3) He's not a 'footballer' in the sense that Stones, Akanji etc and maybe Lewis are. He is to some extent, the odd one out at City in that it's his physical play that earns him a spot. Don't get me wrong I think he's a great player, but once that pace goes I'm not sure he is intelligent enough to keep his spot.
If Bayern come in with a decent offer and he's interested in leaving the Treble Winning Champions I think we should let him go and thank him. We can't keep everyone forever.
I'd rather players left at the top, like Gundogan and Walker in definitely at the top at the minute. When you're at the top, there's only one way down.