I haven't gotten around to reading it yet, so I'm not entirely sure how the novel handles it, but the Sabi fight is just one big joke by Isin. They constantly hype up how strong he is, how it's going to be Shichika's biggest challenge yet. In the anime, the end of episode 3 has a next episode preview showing you glimpses of the (ridiculous) fight to get you excited, which is all completely unique animation that isn't actually seen in the next episode: he's already been defeated offscreen when episode 4 starts, with the characters doing the whole "whew, that sure was tough!" shtick.
As I said, I don't know how the novel does it yet, but personally, I thought the whole thing was hilarious, and is pretty in-keeping with the subversive, meta style of writing that Isin is known for.