SCOTTSDALE, Ariz. -- Major League Baseball plans to emphasize enforcement of the balk rule in 2023 as it implements sweeping rules changes, including a pitch clock that will place more focus on the arcane rule, league officials said Tuesday.

"We have slipped a little bit centrally with calling the rulebook illegal pitches and balks," said Morgan Sword, MLB's executive vice president of operations, at a media briefing to explain the rules in greater depth.

The balk, which is intended to keep pitchers from deceiving runners on base, can be called by umpires for more than a dozen reasons. Balks are assessed only with runners on. Prohibited deliveries with the bases empty are deemed illegal pitches. The import of both is especially acute with the new pitch-timer rule, which mandates a pitcher throw within 15 seconds of receiving the ball with the bases empty and 20 seconds with runners on. If a pitcher balks, runners advance one base.

Stressing the delivery of legal pitches matters because it coincides with the beginning of a delivery, which is when the pitch clock is supposed to stop. Pitchers who violate the rule are assessed a ball as a penalty. Similarly, if hitters are not in the batter's box and facing the pitcher with 8 seconds left on the clock, they will be given an automatic strike.

Trying to understand what constitutes a balk is tantamount to what makes a catch in the NFL. Umpires called 122 balks in 2022, the fewest in a full season since 1973, with some umpires more vigilant than others. Umpire John Tumpane assessed a major league-record three balks in one at-bat to then-Miami left-hander Richard Bleier during a late-September game. Bleier's three balks tied for the major league lead with left-handed reliever Will Smith last year.

A number of pitchers, including Houston's Luis Garcia, Toronto's Kevin Gausman, Boston's Kenley Jansen and the Chicago White Sox's Mike Clevinger, are expected to change their deliveries on account of the new rules.

In the cases of Garcia and Clevinger, their potential violations come from the windup, in which they have significant movement, with Garcia rocking his arms and taking two side-steps before throwing and Clevinger looking like he's dancing with his foot movement. Clock operators are supposed to turn off the pitch timer when a pitcher starts his delivery and, accordingly, umpires have been told that a pitcher is allowed one step to the back or side before moving toward the plate to throw. Gausman's and Jansen's issues are out of the stretch. Gausman would tap his front foot and not come to a fully set position, while Jansen would come set, then twitch his front hip and leg. Out of the set position, the clock stops when a pitcher lifts his front leg.

Those are just two of the ways a pitcher can be called for a balk. If he flinches after coming set, umpires are supposed to call balks. A pitcher drops the ball? Balk. Uncompleted throws to bases constitute balks, as does coming set and separating one's hands as well as perhaps the most borderline call: when left-handed pitchers step toward home plate but still try to pick a runner off first base.

Already the balk was going to see a significant increase because of the new rules. One of them, which limits a pitcher to two "disengagements" during an at-bat -- either pickoff moves, step-offs or a combination of the two -- calls for a balk if a pitcher disengages a third time and does not record an out. MLB's new edicts, which also include limiting defensive shifts and larger bases, will be implemented during spring training games. The new rules will not be in effect for games at the World Baseball Classic, the tournament that will pit 16 countries against one another and is expected to include hundreds of major league players, and players involved will have to adjust on the fly to a suite of changes that people in baseball regard as potentially transformative.

"Frankly," Sword said, "it's probably the biggest change that's been made in baseball in most of our lifetimes."

Sword said the league plans to run explanatory videos at stadiums and a special on MLB Network to further explain the rules to fans. The league hopes spring training offers enough time for players to adjust, as they did in the minor leagues, where they were tested out last year. According to MLB, in the second week of games with the pitch clock, there were 1.73 violations per game. By the fifth week, that had dropped to 0.73, and in the final week, the league said, the violation rate dipped to 0.41 per game.

MLB placing greater import on balks has had significant effects on past seasons. In 1988, when MLB rewrote the balk rule, umpires called 924 -- nearly three times as many as they had in any previous season. The balk rate was halved the next season, and it has held relatively steady, between 122 and 182, since the turn of the century.