Three True Outcomes
From Wiki Gonzalez
The Three True Outcomes = the walk, the strikeout, and the home run.
TTO can be used as an adjective to describe players who seem to do nothing but walk, strike out, or hit home runs.
TTO players are greatly valued (overvalued?) by statheads, because none of the Three True Outcomes are measured very well by batting average, the historic measure of offensive performance. Walks are not in BA at all, strikeouts are no worse than any other kind of out (and superior to GIDPs), and homers only count as much as singles when measured by BA. Theoretically, a TTO player would thus be underrated -- cheaper than a high-average player, but far more productive.
Origin of the phrase is unknown.