After years of debate, professional tennis will begin to rely on instant replay later this month.

Officials from the USTA, ATP, and WTA confirmed the long-standing rumor of replay’s arrival during a press conference yesterday. The initial plan is narrow in scope – players will have a limited number of challenges, and the technology will appear at a small number of hard-court tournaments, including the U.S. Open. But it is clearly a step toward the future tennis deserves, one in which chair umpires are trained to consult replays on every ball that bounces on or near a line, whether a player challenges the call or not.

Hawk Eye, as the technology is known, will make its debut at the Nasdaq-100 Open, a men’s and women’s Masters Series event in Miami that begins March 22. The system offers an almost instantaneous digital redrawing of a ball’s impact on the court via eight court-level cameras. Recent tests suggest it is accurate within three millimeters – much more accurate than the human eye.

At events where Hawk Eye is used, each player will be allowed two challenges a set. If a player challenges correctly, he or she will not lose a challenge. An additional challenge will be awarded if the set reaches a tiebreaker. Challenges cannot be carried over from one set to another. Also, challenges must occur on a point-ending shot, so if a player believes a ball is out, he or she must stop play and ask for a challenge (a player cannot continue, lose the point, and then challenge a ball struck in the middle of a rally). Umpires will have some leeway to review replays without a request from a player in the event that a linesperson cannot see a shot that ends a point and the chair umpire cannot make a decision from sight.

The tours tested the technology at the Hopman Cup in Perth, Australia, earlier this year. If you have any doubts that instant replay is necessary in tennis, data from that event should lay them to rest. Of 83 challenges, players were correct 45% of the time. Umpires often are quite good at their trade, but it’s a trade that increasingly requires powers not available to human beings.

There are few, if any, drawbacks to the technology itself. Officials say its most recent iteration has proved 100% accurate, and even if it is not, it is certainly better than the eye. Unlike the use of instant replay in the NFL, Hawk Eye should not slow down the game: Five seconds is all a chair umpire should need. This is no longer than it takes for an umpire to leave the chair and check a mark on clay, which will remain the practice on clay courts. In fact, replays might increase the speed of play slightly by eliminating the need for a player to plead a case with all the vigor of a criminal defense attorney. Additionally, the replays will be displayed on monitors for fans to see.

There are just two disappointments here. First, the technology, which will cost $100,000 to implement in Miami, will be used only on show courts (the main stadium in Miami and at Arthur Ashe and Louis Armstrong stadiums at the U.S. Open). The same rule will apply if it is added to the components of the U.S. Open Series of hard-court tournaments and the year-ending championships in Shanghai (for the men) and Madrid (for the women).

Second, the challenge system seems needless, since umpires could – and should – make use of this technology in every game, not just twice a set. But Arlen Kantarian, chief executive of professional tennis at the USTA, made it clear that the challenges were merely a starting point that everyone could live with, subject to change in the future.

“We all agreed it was easier to start with a limited set of challenges, with the possibility of evolving to more as opposed to starting with an unlimited number and taking something away,” Kantarian said.

Instant replay had to start somewhere, somehow, and it might as well be this way, even if some players, Roger Federer among them, think it unnecessary. The slow walk to the future has taken an important first step.

tperrotta@nysun.com