Shiryu was above Blackbeard back in Impel Down.
After that, Blackbeard powered up with Gura, Shiryu with Suke.
Shiryu's Awakening is potentially super broken.
Blackbeard could have a direct counter for it though.
He still has to deal with a swordsman Shiryu anyway.
Considering Blackbeard's sloppiness, he may as well stay stronger than him.
We will see after Blackbeard's 3rd DF how things stand.
Unless Shiryu gets a 2nd DF too.