José Rafael Santiago Alfonso (born August 15, 1940, in Juana Diaz, Puerto Rico) is a former right-handed pitcher in American Major League Baseball.
Possessor of an outstanding curveball, Santiago reached the American League in 1963 with the Kansas City Athletics. His contract was sold to the Boston Red Sox after the 1965 season, and he became a key member of pitching staff of the 1967 Red Sox, posting a 12–4 record with a 3.59 ERA in 50 games. He was largely a middle relief pitcher that season, starting only 11 games, and compiled an 8–3 mark in relief with five saves. However, he also made several important starts, including Game 1 of the 1967 World Series, which he lost to Hall of Famer Bob Gibson, 2–1, accounting for the only Boston run with a home run in his first World Series plate appearance.
Although Santiago lost both of his World Series decisions to the St. Louis Cardinals and compiled an ERA of 5.59, he began the 1968 campaign in the Boston rotation, compiling a 9–4 record with a 2.25 ERA in 18 starts before an elbow injury ended his season. The injury effectively ruined his major league career. After that, he appeared in only 18 more games during 1969 and 1970, and never won another major league game.
Santiago ended his majors career with 163 appearances, 34 victories and 29 losses and an ERA of 3.74. He also was selected to the 1968 MLB All-Star Game.
In 1979, Santiago managed in a short-lived Class AAA circuit, the Inter-American League, as skipper of the Puerto Rico Boricuas. His club won 16 of 55 games (.291), ending sixth and last in the six-team league, and folded June 17. Thirteen days later, the entire league shut down.