On June 4, Birtsas accomplished the rare feat of striking out four batters in one inning. Regardless, following a poor performance against the Atlanta Braves on June 20, Piniella seemed to lose faith in Birtsas. Birtsas saw little work in key situations in the second half of the season, and was optioned down to triple A toward the end of July. He was recalled in September, and was part of the Reds' post-season roster, but did not make an appearance in the 1990 National League Championship Series with the Pittsburgh Pirates or World Series against the A's. The Reds were 0-12 in Birtsas' final twelve regular season appearances.