One is assigned at a monitor to watch a particular game, meaning that if there are 14 games on a particular night, 14 officials are utilized, said Frank Brown, a spokesman for the league.
Also, one official staffs a replay booth located on-site at each arena, which is equipped with high-definition cameras placed high above the two goals. While 1,230 games are played each regular season, only about a dozen are not televised on either the national or local level.
In that case, a second replay official is stationed in the arena and disputed goals are determined on-site, Brown said.
The National Basketball Association uses replay just to determine the validity of last-second shots, as opposed to time left on the game clock. Beginning with the 2007-08 season, the NBA began permitting referees to use instant replay to review altercations and flagrant fouls.
Only the National Football League uses replay extensively to review disputed plays. In the NFL system, a head coach can ask to review a call at the risk of losing a timeout if it's not reversed.
The NFL was one of the first major sports leagues to embrace instant replay, welcoming the technological advent by incorporating it into the television-friendly sport in 1986 and then revamping its use extensively in 1999.
Instant replay has been a boon to the NFL, though not everyone loves the concept as it relates to baseball. Cubs manager Lou Piniella was among those who dissented when polled on instant replay this season, saying, "When the NFL coaches drop that red handkerchief [for a review], I go to the refrigerator for about four, five minutes.
"My thoughts are, the game's been this way for 100 years and it's done well," he said. "Players, managers and coaches are all going to make mistakes, as umpires are, and it all evens out. I don't see the need for replay on home runs or anything else."
But instant replay has improved steadily in the NFL with years of use. The 2007 NFL regular season saw a record number of instant replay reviews, challenges and reversals. Last season, 327 plays were reviewed in 256 games, the most since the inception of the instant-replay system.
Out of a record 250 challenges by head coaches, 122 were reversed -- for a 48.8 percent reversal rate. That's up from 45.1 percent in 2006 and 29 percent in 1999.
The NFL's use is extensive. Challenges can be made on a variety of game situations, including but not limited to scoring plays, complete or incomplete passes, interceptions, boundary calls, fumbles and forward passes. In April, owners voted to allow instant replay of field-goal attempts that go above or below the crossbar or inside or outside of an upright.
Those multiple uses would be too much for MLB to incorporate, opined Angels manager Mike Scioscia.
"I think it should be limited to a home run or fan interference," Scioscia said. "There are so many things in baseball that you can question that it would be almost dysfunctional."
Some NCAA sports and major tennis tournaments also utilize replay in some form, with the Big Ten Conference beginning use of football instant replay in 2004, and hoops using it on a limited basis. Tennis tournaments have moved technology past the video stage, permitting use of the Hawk-Eye 3D rendering computer program to spot close or controversial line calls.
The Little League Baseball World Series held Aug. 15-24 in Williamsport, Pa., had instant replay in place for the first time this year, with the help of ESPN's cameras.
For tournament rules, the use of video replay was limited to the case of a batted ball that left the field of play at or near the outfield fence, or should have been ruled out of the field of play at or near the outfield fence.
"As we have seen even in the professional ranks, these calls are among the most difficult for umpires to make for a variety of reasons," said Stephen D. Keener, the president and CEO of Little League Baseball and Softball.
"Using video replay, in very limited situations and on an experimental basis for one year, simply gives us a better chance to get these calls right. In 2009, we will evaluate the program and decide if it will be used again."
For a change, MLB will follow the kids. Rockies manager Clint Hurdle believes that the time to embrace instant replay has come.
"We live in a technological society now," Hurdle said. "We can get it right. The guy at home sees it right. That, for me, is where it gets confusing. You can sit in your chair at home and make the right call, but the man getting paid, who's the expert, who's done it for 20 years, is put in a box where you don't know."