The Tigers announced the move Wednesday.
Santiago appeared in 19 games -- including two starts -- last season for the Chicago White Sox and New York Mets. He went 1-1 with a 6.68 ERA. In 2018 with the White Sox, he was 6-3 with a 4.41 ERA while pitching mostly in relief.
The 32-year-old Santiago is 47-50 with a 4.14 ERA in his major league career.