A player, manager, umpire and scout for more than 40 years in the National League, Hank O’Day remains the only person to serve the league in so many capacities.

But it was as an umpire where O’Day made his greatest mark on history in some of baseball’s greatest games. And it’s as an umpire that O’Day earned election to the National Baseball Hall of Fame, just the 10th arbiter to be inducted.

On the gridiron, Cal Hubbard pioneered the modern linebacker position and was one of the most intimidating players in the National Football League.

But it was his remarkable ability to arbitrate the action on the baseball diamond that propelled Hubbard to become the only man in both the Pro Football and Baseball Halls of Fame.

“I’m just a big old country boy who hated to sit on the sidelines,” Hubbard said. “I wanted to be in the middle of the action.”

He was so easily identifiable that no sleeve number was even necessary.

The silver hair, the methodical-yet-authoritative signals. A presence that earned him the nickname “god.”

Tune in to a high-profile Major League Baseball game in the 1970s or 1980s, and No. 8 – Doug Harvey – was likely to be behind the plate.

While the word “umpire” most often evokes images of an older sage in the minds of baseball fans, fresh-faced Billy Evans was anything “old” when he debuted as an American League umpire in 1906.

At a remarkable 22 years of age, Evans became the youngest umpire in major league history and began a 22-year career in which he worked six World Series.

Furthermore, Evans was a baseball renaissance man. He was an accomplished sportswriter at the same time he was an umpire, and later became a front office executive for three major league teams.

Tom Connolly officiated the first American League game in 1901 and saw the league’s evolution from upstart to respected equal of the National League during the next three decades.

Known for his calm and dignified demeanor, Connolly possessed a remarkable ability to control the game, so much so that he once went 10 consecutive seasons without ejecting a player during one of the toughest eras in baseball history.

“A well-groomed, alert umpire adds dignity to a ball game,” Connolly once explained. “And a good official is one who never attracts attention.”

Nestor Chylak recovered from a World War II accident that nearly rendered him blind to become the model umpire of the post-war era.

Chylak, a son of Ukrainian immigrant parents, was serving in the United States Army during the infamous Battle of the Bulge when he was wounded by shrapnel from an exploding shell. He was hospitalized for eight weeks with bandages over his eyes before recovering with his eyesight intact. He was later awarded both the Silver Star and Purple Heart for his courage in battle.

Many major league players, at some point during their careers, have claimed they could call a game as well as the umpires.

In a 1935 game between the Chicago White Sox and St. Louis Browns, White Sox player Jocko Conlan got the rare chance to do just that – and then never looked back.

Conlan was a reserve outfielder during that fateful July day when umpire Red Ormsby was overcome by the heat. Since there were only two umpires assigned to the game, Conlan was asked to fill in.

Respected for his remarkable ability to “call ’em right,” umpire Bill McGowan developed a reputation for integrity and accuracy that earned him the nickname “No. 1.”

McGowan introduced flamboyant gestures behind the plate that captured the attention of players and fans alike. His enthusiasm never waned over his 30 years in the American League, including a string of 2,541 consecutive games in which McGowan did not miss a single inning on the diamond.

While he was known for his fiery personality, McGowan rarely went over the line in his interactions with players.

Al Barlick’s rise to becoming one of baseball’s most revered umpires began in a coal mine in Springfield, Ill.

In 1935, Barlick was helping his father in Springfield’s Peabody mine when a friend asked if he could fill in as an umpire for the local municipal league games. Five years later, Barlick debuted behind the plate in a doubleheader at Shibe Park, becoming one of the youngest umpires in major league history at age 25.

During the next 27 seasons as a National League umpire, Barlick would call seven All-Star Games and seven World Series.

"Your job is to umpire for the ball and not the player." – Bill Klem

While the mark of a good umpire is often to go unnoticed throughout the course of the game, National League umpire Bill Klem was a colorful exception.

Known affectionately as “The Old Arbiter,” Klem was a pioneer for umpires across the major leagues during his 37 years on the diamond. He was the first umpire to wear a chest protector, and also one of the first to use visible arm signals to coincide with his calls.