The recent controversy surrounding Anthony Rizzo of the Cubs and his hard slide into Padres catcher Austin Hedges has once again revived discussion of MLB's revised rules governing plate-blocking and plate collisions. 

By way of reminder, the rules were changed somewhat drastically prior to the 2014 season. Now, a runner isn't allowed to deviate from his path to the plate in order to make contact with the catcher, and in turn the catcher isn't allowed to block any part of the plate unless he's got the ball or is in the immediate act of receiving the ball. In broad terms, the runner when sliding must first make contact with the ground in any effort to touch the plate. 

So how did we get here? Time was when, runners routinely blew up the catcher at the plate in a sporting attempt to dislodge the ball and thus prevent any tag. Catchers by and large accepted this as the cost of doing business. This wasn't a part of baseball through much of the last century, but eventually it became a sanctioned part of the close tag play at the plate. 

As for how we got from there to here, it's a methodical journey, of course, but a few notable plate collisions stand out as advancing the push for change. Let's have a look ... 

1. Pete Rose vs. Ray Fosse, 1970 All-Star Game

As noted above, violent home plate collisions weren't a part of the game in the early days of baseball history. Rose's decking of Fosse in an exhibition game, though, seemed to give sanction to the practice. 

2. Bo Jackson vs. Rick Dempsey, 1987

This was perhaps an early sign that the strength and power of the modern athlete made collisions all the more dangerous. It's fitting that this clip ran during one of Jackson's NFL games.

3. Ken Caminiti vs. Greg Olson, 1992

In one of the ugliest collisions ever, Olson suffered a broken ankle, was down on the field for more than 10 minutes, and had to be carted off in a neckbrace and inflatable cast. The violence of the Caminiti-Olson collision made an impression.

4. Scott Cousins vs. Buster Posey, 2011

This collision broke the leg of Posey, then one of the game's most compelling young stars. That Cousins felt justified in veering so far out of his path to initiate contact with Posey suggested to the league that things had gotten out of hand. 

5. Josh Harrison vs. Yadier Molina, 2012

A little more than a year before new collision/plate-blocking rules were put into place, the violent collision between Harrison and one of the great defensive catchers in MLB history provided an acute reminder that change was on the way.