John (Jack) Albert Pfiester (May 24, 1878 in Cincinnati, Ohio – September 3, 1953), is a former professional baseball player who pitched in the Major Leagues from 1903 to 1911.
Pfiester finished with a 1.51 ERA in 1906 (one of the best rookie seasons by any pitcher since), and a 1.15 ERA in 1907. His career ERA is 2.02, 3rd lowest among pitchers with 1,000+ innings thrown, and he had a .617 winning percentage. On September 23, 1908 against the New York Giants he pitched a complete game, allowing five hits, all with a dislocated tendon in his pitching forearm. He had to be assisted off the field a few times after throwing curve balls. And as soon as the game ended he went to Ohio to be treated, his tendon snapped back into place by trainer Bonesetter Reese.
Although Bonesetter got Pfiester throwing again, it would prove to be only a matter of time before the wear and tear got to Pfiester. In 1909, Pfiester posted 17 wins and a 2.43 ERA in his last full season. Over the next two years he would make 20 more appearances as a major league pitcher, and by the age of 33 he was done. After Pfiester's playing career ended, he and his wife settled in Ohio with their son, Jack Jr. Pfiester died in Loveland, Ohio, at the age of 75.