Gastright's best season was 1890 when he won 30, lost 14, and had a 2.94 earned run average for Columbus. His ERA was seventh best in the American Association, his 30 wins were third best, and his four shutouts placed him second. On October 12, he pitched an 8-inningno-hitter against the Toledo Maumees, winning 6–0.
Another notable season for Gastright was 1893, when his combined mark of 15–5 while pitching for Pittsburgh and Boston gave him a winning percentage of .750, best in the National League.