How has instant replay changed baserunning?

Last offseason, Major League Baseball greatly expanded its use of instant replay review. The underlying goal was to reduce the impact of umpire error in determining outcomes. While not yet perfect, games and, indeed, pennant races are now more purely determined by objective performance than at any other point in the history of the sport.

The expansion of video review allowed managers to challenge tag plays. Last season, 209 tag play calls were reversed, with 43 more already this year. On average, one tag play is corrected every 12 games, or slightly more than one every day of the season. So far this year, a shift of 18 percent in win expectancy is directly attributable to reversed tag plays in games involving the Pirates. (The Pirates have gained 14 percent in win expectancy due to two successful challenges, while losing four percent on reversals that have gone against them.)

However, the impact of reviewing tag plays is not limited to reducing the impact of umpire error. Indeed, according to some players and coaches, it is also fundamentally changing play on the base paths.

"Absolutely more physical," Clint Hurdle said of the affect instant replay is having on baserunning. "It has gotten physical around the bags."

Reds first base coach Billy Hatcher pointed to Andrelton Simmons' controversial late slide into Yunel Escobar as a sign of things to come.

"Did you see the other day with Atlanta and their shortstop slide into third base and Washington got pissed off about it?" Hatcher said. "He slid late, but he slid hard in. Usually guys just slide in and they just tag him and it's a gentleman's game. Not anymore. ... I like the way Simmons went into the bag."

Neil Walker summarized the situation. "I guess you could say it's more dangerous," he said.

No longer a gentleman's game

Why is the action around the bases becoming more physical, and how does that relate to instant replay? The answer begins with a subtle, but noticeable, transformation in tagging techniques. More precisely, instant replay is causing the slow extinction of less aggressive tagging methods. The swipe, pop and phantom tags are disappearing because they are less efficient at guaranteeing contact with the runner.

"You definitely have to stay down longer and make sure you tag him, because if you don't tag him, he's going to be safe," Pete Kozma said.

As Jordy Mercer explains, infielders now have to stay down and "get nasty" with the runner.

"[In the past], you could do a lot of swipe tags and pop it and if you didn't touch him it looked like you did, and they were out no matter what," Mercer said. "There's a lot of guys you just wanted to get the tag in and get the hell out of the way. But now you got to get in there and just kind of get nasty with it. That's just part of the game. That's how it's starting to change. You've got to change with the game."

Neil Walker points out that the need to make indisputable physical contact with the runner is putting fielders in precarious situations and changing their approaches.

"With instant replay, it's hard to swipe tag now," Walker said. "And it's already happened once this year, maybe Chicago. A guy slid in and it was a close play, and I might have been able to just put the glove down, but I would have got my hand smashed. And most of us don't want that to happen, although the situation may dictate that. But a lot of times we're so used to swipe tags (and) phantom tags, and we were able to get away with that. But now we can't get away with that."

Along with staying down and making contact, fielders are also holding their tags longer in order to catch runners sliding off the bag.

"[Gregory Polanco's] been out a number of times, been safe and then been out coming off the base," Hurdle said. "In the past, I don't know if those situations would have ever happened because guys would just slap a tag and get out of town. Now they slap a tag and hold it while that guy's trying to hold onto the base and maintain balance."

The combination of fielders staying down and holding tags longer is causing baserunners to adjust their sliding technique in response. Specifically, the hard, direct pop-up slide is growing in popularity and utility.

"It used to be if the ball beat you there, the ump called you out regardless of how you slid," Hatcher said. "So now it's not that. So you're going to replay everything, so I want my guys to slide in hard, because I want the middle infielders to do the little fake tag where they hit the ground and get out of the way. If you're coming in here slow, they're just going to keep it down there. You're coming in hard, they're getting out of there. And when they get out of there they're missing the tag, which is exactly why I teach my guys to go in hard and [pop up]."

‘Old-school' hard sliding

We've all seen the black-and-white photos of Ty Cobb's famously hard, and often dangerous, sliding technique. While Hatcher says he isn't teaching his players to injure anyone, he's emphasis is clear: he is teaching a return to what he calls ‘old school' sliding.

"Infielders don't like contact, so I'm teaching my guys to go back to old school and teaching my guys the pop-up," Hatcher said. "Hal McRae and some of the things they taught me -- slide in and bump it up. I mean, guys (are) trying to get the tag on you when you're stealing bases. You don't want the second baseman and shortstop comfortable fielding the ball."

Hatcher discussed instant replay and a new sliding approach with his players during spring training.

"It is connected to instant replay because you see guys now keeping their glove on them," Hatcher explained. "How many times are you going to see a guy keep a glove on them if a guy is coming in hard and popping up? So that is what I'm teaching my guys."

Peter Bourjos sees the benefits of the pop-up technique, as well, and it is something he is trying to incorporate into his running game.

"If you are popping up it is harder for them to push you off the bag, and you're coming in there with some force to where they might not be able to stay in there as long," Bourjos said. "You may be able to knock them off a little bit. So, yeah, you definitely want to try to pop up and stay on the bag as long as you can. Because replay has really changed that aspect of the game."

Pirates third base coach Rick Sofield said that he hasn't tried to alter his players' slides too much because of instant replay, but he acknowledged that "there are things we're trying to do," which includes utilizing the pop-up technique more often.

"We're trying to be more direct and use that pop-up, especially if we're looking for that errant throw versus the sweep and the hook slide," Sofield said. "But there's no question we're trying to stay a little bit longer on the bag and in the alley."

Sofield also observed that things are going to get rougher on the base paths, as both fielders and baserunners adjust their techniques.

"Guys are sliding in stronger and more direct to make sure they keep contact with the bag," Sofield said. "Knowing all this, the defenders stay there longer in order to get it. There's going to be more collisions."

Players bracing for more contact

As fielders and baserunners adjust to and optimize their techniques for instant replay, they are also preparing for a more physical game.

"I can definitely see guys coming in a little harder," Kolten Wong said. "Obviously, as an infielder, you're aware of that and you try to put yourself in the best situation and not get hurt. But at the end of the day you have to make sure you get that tag down."

Walker is aware of the need to protect himself now more than in the past.

"Yeah, they definitely can be [more dangerous]," Walker said. "Something you've got to be aware of is just obviously you want to protect yourself. You don't want to find yourself with cleat marks in your hand."

Runners, meanwhile, have to get used to fielders holding hard tags on them longer.

"I think before they were just going to slap the tag on you and that was it, that was the end of it," Bourjos said. "Now they're holding it on there. It's to the point where you're like ‘Get it off! It's been on there for 10 seconds. Give me time or something.'"

Conclusion: Getting the call right leads to adjustments

Instant replay of tag plays helps ensure the right calls are made, and it creates more outcomes that are based purely on player performance. This, for players like Josh Harrison, is still the most important change.

"I just think it gives you a chance to be for sure," Harrison said. "There are times when we slide in, and they call us out, and we're like, 'Hey man, I got in there,' and they overturn it. And there are sometimes where you're like, ‘Man, I don't think he tagged me,' and the replay shows, ‘Okay, they got the call right.' It leaves the chance to get things right."

As Brandon Phillips put it, the game changes and adjustments simply have to made. The keys for fielders today are simply to be more precise with their tags, and to make sure baserunners who should be called out are, in fact, called out.

"But now you have to make sure to try your best not to make any mistakes because people can reverse the call," Phillips said. "So that is one that does cross everybody's mind. They want to make sure that they do make things happen, that they make sure they do get that guy out."

So, instant replay has changed the game in intended and perhaps some interestingly unintended ways. As Clint Hurdle succinctly summarized this new era of tag play replay: "There is no doubt it's become more physical around the base. You got to get down there and stick your nose in there and stick with the play. Both sides."

(Statistics courtesy of Baseball Savant)