While in college he became the first 20-game winner in a season (in 22 starts) and threw 234 strikeouts (both national records).
[citation needed] Tatsuno was selected in the 2nd round of the regular phase of the June 1979 draft by the San Diego Padres.
In 1982 he played for the Brewers' AA affiliate, the El Paso Diablos of the Texas League, going 7–2 with a 6.42 ERA and walking more than a batter an inning.
In 1983 he was demoted to the Single-A Stockton Ports of the California League, going 10–6, 3.24, but Milwaukee released him.
After not pitching the two previous years, Tatsuno resurfaced briefly with the Hawaii Islanders of the Pacific Coast League, the 1986 Triple-A affiliate of the Pittsburgh Pirates and 1987 Triple-A affiliate of the Chicago White Sox.