While Rodríguez was on the winter roster for the Reds, he was waived by the team in December. On December 20, the Pittsburgh Pirates claimed him off waivers. He was scheduled to be in camp by February 21, but due to visa problems, he did not arrive in camp until March. He split time with the Buffalo Bisons and the Pirates that season. With Buffalo, he pitched in 48 games and posted a 4–3 record and a 3.00 ERA. During the 1991 Pittsburgh Pirates season, he pitched in 18 games and had an ERA of 4.11. He also had one appearance during the 1991 National League Championship Series, allowing three runs in one inning against the Atlanta Braves.