A potential grade and a half jump between present and future grades is more than I would usually be willing to put on a prospect, but Tuivailala is a converted position player who hasn't been pitching very long, so there's a lot of room for growth. He is still very raw and is very much in the middle of the transition from thrower to pitcher. He does, however, show glimpse of being a player who is succeeding at that transition. The arm is fantastic, and generates premium velocity with ease. His slider is still quite raw, but he generates good spin and movement with the pitch. Once he learns to command it better, it can be a second plus pitch.

For Tuivailala, however, that's it. He has no off-speed pitch and could struggle against left-handed hitters if he doesn't come up with something to combat them - perhaps a cutter. That said, he does have the ability to miss bats that could allow him to pitch in late innings. If he doesn't develop something to throw to lefties, he'll settle in is an effective right-handed specialist, but even a show-me offering against off-handed hitters could be enough to allow him to pitch late in games.