Baseball introduces a technical replay review system for calling balls and strikes

For more than a century, baseball home plate umpires have called a ball or a strike based on a vague, loosely defined definition of the strike zone.

These individual calls decided at-bats, games, seasons and penalties — and, naturally, sparked endless controversy.

Now, for the first time, this season Major League Baseball is implementing a review process where players can challenge a strikeout call. Description: For the first time the location of the strike will be explained and there will be a specific answer in the discussion.

The Automated Ball-Strike (ABS) challenge program, tested in the minor leagues and MLB spring training, will make its debut Wednesday evening in the MLB season opener, when the San Francisco Giants play the New York Yankees – coincidentally in America’s high-tech capital.

After every pitch, when the umpire calls a ball or strike, there will be a two-second window in which the batter, batter or catcher can initiate a challenge.

Once a review is requested, the pitch’s scoreboard will display the system’s decision as to whether the pitch passed the strike zone. Everyone will have to wait in breath, like tennis and the challenges of incoming/outgoing calls.

Each team will get two challenges in the game, and they will keep them if they are correct.

But in order for baseball to create its own system, MLB had to define its strike zone, which has been a moving, target since the beginning of the game.

Regarding the rule change, this is a major change in baseball, which is expected to change the way of playing and the strategy, unlike when the American League adopted the designated hitter in the 1970s.

“I think [the ABS system] it’s more important than DH, and it’s more of a bad strikeout rule at the turn of the last century,” MLB historian John Thorn told NBC News.

What is the new strike zone?

Before Wednesday night, throughout the history of baseball, the strike zone has been the focus, right down to the umpire’s judgment. The claim has recently been defined as the area above home plate, bounded at the top by the area between “the batter’s shoulders and the top of the uniform pants” and below by “the point below the kneecap.”

“Umpires have traditionally called a variable, right? It depends on the count, the situation of the game, the score, all those things,” said MLB vice president of on-field strategy Joe Martinez. “The strike zone tends to grow and contract based on those kinds of things.”

Now, if a strike call is challenged, the strike zone will be strictly defined based on the height of the batter. A strikeout is now defined as a pitch that travels over home plate and is between 27% and 53.5% the height of the batter’s height.

Under the new system, if an opposing pitch presses against any part of this figurative “pane of glass” that rests in the middle of home plate, that will be called a strike, Martinez said.

What are the benefits?

Why does baseball need replay review?

Look no further than the latest World Baseball Classic. In the semi-final between the United States and the Dominican Republic, the game ended with a called third strike, on the field that appeared to be out of bounds.

That platform was “3 inches below ground, [a replay system] it would have changed everything,” said Miami Marlins pitcher Liam Hicks [ABS] it saves a lot of time from going the wrong way. So I think I’m a fan of it.”

But even a missed call that isn’t the fourth ball or the third strike can have a big impact. For example, if the count is 2-1 and the batter does not swing in the right field, his outcome will be significantly changed on the next call.

If the ball is called and the batter walks before the count is 3-1, that batter in 2025 has a .255 batting average, .592 on-base percentage, .453 slugging percentage and 1.045 OPS. Or, in other words, that average hitter, with a 3-1 edge, is like all-world slugger Shohei Ohtani, who recorded a 1.014 OPS last season.

But when that umpire calls a strike and the count is tied at 2-2, everything turns upside down. That hitter, 2-2 last year, went on to have a paltry .178 batting average, a .286 on-base percentage, an anemic .291 slugging percentage and a .577 OPS.

Of all MLB hitters last year with enough qualified plate appearances, the lowest OPS was recorded by Milwaukee Brewers shortstop Joey Ortiz (.230/.276/.317) at .593.

What is the strategy?

Interestingly, players will have to decide whether to challenge each other. They can’t take direction from coaches, teammates or the rowdy fans shouting in the stands.

“A player’s decision to throw a challenge should not be unheard of” and “if someone is yelling in the dugout, if another player is on the field, hitting his head, the umpires have the power to deny the challenge,” said MLB official Martinez.

Each team can continue to challenge until they are wrong twice, so these important appeals should not be used voluntarily.

The manager of the Miami Marlins, Clayton McCullough, said that his team will prevent its strikers from calling the challenge, although they are allowed, leaving the decision to the hunter. The pitcher is standing about 60 1/2 feet from home plate after all, much farther than the catcher.

“Our players will not be able to challenge,” McCullough said. “We’re going to put a lot of effort into all of our catchers who are good at doing this. It’s led us to create training areas in camp for them, our catcher in particular, to use a lot of bandwidth in training with the automatic strike zone.”

In triple-A last year, challenges were 50% successful, and 51% the year before that.

This spring, most major league players and managers said they planned to save appeals for late innings and other important points of the game, known as “high-level” situations.

In triple-A games in 2025, the highest percentage of pitches came in the ninth inning (3.5% of all pitches), and the least came in the first inning (just 2.1%).

“[What] We tried to pressure them during this camp, of course, we would like to be more successful in answering the calls,” said McCullough.” And, perhaps most importantly, we want to be challenging at the right times.”

But on the contrary, first-year San Francisco Giants manager Tony Vitello said he wouldn’t worry about his players being aggressive in using challenges even early in the contest.

“I think the biggest thing is you don’t want to leave them on the table,” said Vitello, the highly successful University of Tennessee coach who is believed to be the first MLB manager with no previous major league experience.

If you see something you feel like, ‘Oh, I know for sure it’s off,’ you might as well stop it.”

A learning curve for fans

In a spring training game last week between the St. Louis Cardinals and Miami Marlins, many fans reached by NBC News did not know that MLB had entered this system challenge for 2026 – even if the pregame lesson was played on the scoreboard at Roger Dean Chevrolet Stadium in Jupiter, Florida.

“I’m a cultural person and I don’t like it,” said Dallas resident Heather Garrison, who was at the game to see her son, Marlins bullpen pitcher Tanner Garrison. “I like the old fashioned way where you hope they call and you go with it and in the end, it all comes out.”

Another Jupiter fan that day, Jordan Waxman, said he would prefer that any challenge decision be made by a human, rather than a computer, as in the case of safe/out calls that are reviewed at the MLB replay center in New York.

“I don’t like it [the new replay system]”I don’t like anything to do with AI,” Waxman said. [an automated system] until now. It just removes from the history of the game. I’d rather they call New York a challenge than a computerized one. You start getting computers involved, what’s next?”