Rather than ban home plate collisions outright, Major League Baseball and its players adopted a rule limiting them this season.
In what both sides said was a one-year experiment, the rule allows collisions if the catcher has the ball and is blocking the runner's direct path to home plate, and if the catcher goes into the basepath to field a throw to the plate.
The new rule, 7.13, states "a runner attempting to score may not deviate from his direct pathway to the plate in order to initiate contact with the catcher (or other player covering home plate)." A runner violating the rule shall be declared out, even if the fielder drops the ball.
Along with the rule, the sides agreed to a pair of comments that umpires use to interpret the rule. The first comment says, "the failure by the runner to make an effort to touch the plate, the runner's lowering of the shoulder, or the runner's pushing through with his hands, elbows or arms, would support a determination that the runner deviated from the pathway in order to initiate contact with the catcher in violation." The comment says players who slide appropriately are not in violation of the rule.
The second comment says that "unless the catcher is in possession of the ball, the catcher cannot block the pathway of the runner as he is attempting to score." The runner shall be declared safe if the catcher violates that provision. In addition, it is not a violation "if the catcher blocks the pathway of the runner in order to field a throw, and the umpire determines that the catcher could not have fielded the ball without blocking the pathway of the runner and that contact with the runner was unavoidable."
The rule serves as a compromise between the league and the player's union.
Sources told ESPN The Magazine's Buster Olney that Major League Baseball's playing rules committee adopted a must-slide/no block rule which would have required the runners to slide and the catchers to give the runners part of the plate.
However, the MLBPA would not approve that rule for 2014 because they felt that there was insufficient time to train catchers and runners to adjust their behavior before the start of the season. The discussion over that particular distinction is why spring training opened without the rule fully defined.
The umpire crew chief can use the new video-review system to determine whether the rule was violated.
Debate over plate collisions has intensified since May 2011, when San Francisco's Buster Posey was injured as the Marlins' Scott Cousins crashed into him at the plate. Posey, an All-Star catcher, sustained a broken bone in his lower left leg and three torn ligaments in his ankle, injuries that ended his season.
"Just reading through it, the main thing it does is eliminate the malicious collision," Posey told ESPN's "Baseball Tonight" on Tuesday morning. "If the catcher is not set up right on top of the plate, it doesn't allow the runner to run through him."
Posey said the tweak to the rule would not alter the way he prepares for the season as a catcher or as a baserunner.
"For the most part, I think it'll stay pretty much the same," Posey said. "We've never been taught to set up right on top of the plate; we've always been taught to give the runner a little bit of the plate.
"[As a baserunner], my mindset, when I'm coming around third, is to slide hard and late."
"It stops guys just going out of their way just to try to dislodge the baseball when [catchers] have the plate," Rangers manager Ron Washington said.
Hall of Famer George Brett, the Kansas City Royals' vice president of baseball operations, said he doesn't like the rule even though he understands that the objective is to reduce injuries.
"I'm not a big fan of it," Brett told ESPN.com. "Catchers are taught to put their foot right in front of home plate, and the plays are bang-bang. I like the collision.
"I don't sit around at home at night and think about it. This is the first time I've thought about it since two months ago when somebody told me, 'They can't run into catchers anymore.' I said, 'That sucks. I love that play.'"
A runner who violates the rule will be declared out even if the catcher drops the ball. If a catcher blocks the plate without possession of the ball, the runner will be safe. However, a catcher may block the plate to field a throw if the umpire determines he could not have otherwise fielded it and thus contact with the runner could not have been avoided.
"We believe the new experimental rule allows for the play at the plate to retain its place as one of the most exciting plays in the game while providing an increased level of protection to both the runner and the catcher," new union head Tony Clark said. "We will monitor the rule closely this season before discussing with the commissioner's office whether the rule should become permanent."
Baltimore Orioles catcher Matt Wieters, who was steamrolled at the plate by Sean Rodriguez in 2012 and Ryan Kalish in 2011, is one of the biggest supporters of the rule change, although he'd like to get clarifications from Major League Baseball on exactly what is and isn't permitted.
"There are always going to be catchers who want to leave it on the field," he said. "You want to be strong for your team. And stopping runs is the most important part of this game. It's whoever scores the most runs. So you want to be able to stop those runs at any cost.
"But the bigger thing that I think really comes into play here is you look at the NFL and the effect that concussions have. You know, we're not just talking about a career. You're not just talking about missing a season with an injury. You're talking about a couple of head-to-head collisions, and you could have quite a bit of memory loss and quite a difficult time functioning later in life. And for me, I think that's the one issue I'm glad is hopefully going to be straightened out."
Orioles manager Buck Showalter attended a briefing on the rule by baseball officials Sunday. And as someone who still cringes when he thinks of some of the hits Wieters has taken, Showalter is grateful for a rule that aspires to all but eliminate "the cheap-shot collision."
"We're talking about where the [catcher] is completely exposed, doesn't have the ball and some guy hunts him," Showalter said. "We've had it happen with Matt a couple of times. And as you remember, we were real unhappy about it. I can still remember the players who did it. With no intent to score. Had the plate given to him. Could have slid. And just [hit him] very maliciously. We're going to get that out of the game."
Wieters, however, wanted to make it clear that this isn't a rule merely designed to protect catchers.
"You know, catchers don't want to see runners getting hurt, either," he said. "So you want to be able to protect the runner, too. And I think that's part of the issue of why it's taken so long to put something together. You've got to be able to protect both parties. You can't just say, 'The catcher can do whatever he wants, so now you're going to have a bunch of runners getting hurt.' It's a fine line of trying to keep the game the same but at the same time coming up with a rule that also eliminates some injuries."
And he and Showalter both believe baseball accomplished that Monday.
"You're probably not going to see, with the naked eye, a lot of the changes," Showalter said. "Just hopefully, we won't be showing on 'Baseball Tonight' these violent collisions that shouldn't have happened."
ESPN.com's Jerry Crasnick and Jayson Stark, ESPNDallas.com's Richard Durrett, ESPN The Magazine's Buster Olney and The Associated Press contributed to this report.