Bill Hohn has retired after 23 years as a major league umpire and been replaced by Todd Tichenor. Hohn missed the 2011 season because of a back and neck issues. The 56-year-old worked the division series in 1996, 1998 and 2005, and the 1994 All-Star game. He was behind the plate for Hideo Nomo's no-hitter for the Los Angeles Dodgers at Colorado on Sept.