Thomas Francis Hallion is a retired Major League Baseball umpire who worked in the National League (NL) from 1985 to 1999 and in both major leagues from 2005 until 2022. He was promoted to crew chief in 2010. Hallion has worn number 20 during his MLB career. He resigned from the NL in 1999 as part of a failed mass bargaining strategy, but he was rehired by MLB before the 2005 season.
Hallion in 2011
In baseball, the umpire is the person charged with officiating the game, including beginning and ending the game, enforcing the rules of the game and the grounds, making judgment calls on plays, and handling the disciplinary actions. The term is often shortened to the colloquial form ump. They are also sometimes addressed as blue at lower levels due to the common color of the uniform worn by umpires. In professional baseball, the term blue is seldom used by players or managers, who instead call the umpire by name. Although games were often officiated by a sole umpire in the formative years of the sport, since the turn of the 20th century, officiating has been commonly divided among several umpires, who form the umpiring crew. The position is analogous to that of a referee in many other sports.
An MLB umpiring crew meeting with the managers from each team before a 2017 game
Home plate umpire Malachi Moore reviews the lineup cards from both teams before a 2016 minor league baseball game
Base umpire Stu Scheurwater calls Eduardo Escobar safe.
An umpire calling a strike on Barry Bonds (#25)