Yabu kind of reminds me of Leon Powe in his development. Came into the league a physical specimen with really good instincts but basically no awareness of what he was doing out on the court. Powe was basically unplayable his first year and a half in any real capacity, because when you asked him to do anything within the system he either slowed down as he thought it through, or he simply missed his rotations. But then suddenly it clicked, and he was able to unleash his talents because he knew what he was doing.
That is the same progression I have seen with Yabu so far. Super raw, and clearly thinking things through early in the season, but now that he has come back he is starting to react rather than think, and you are starting to see the impact he can have with his unique skills and instincts.
I don't think he is ready yet, but he has shown enough in these last few games that I think it is very possible that he could legitimately be counted on next year to fill in for either Baynes or Monroe, one of whom might have to go to stay under the tax.