About Shamrock

I'm rewatching The Wire, and one thing I've never really understood is Shamrock's position in Barksdale organization.

He's basically Stringer's right-hand man and seems to hold a pretty high-ranking position. But... what exactly is he good at?

He's not a fighter or enforcer like Wee-Bey. He's not particularly intimidating, and we don't really see him handling violence or doing the kind of dirty work that would justify his status.

He's also not a particularly good administrator either.

So why is Shamrock so high up?