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Kevin Kiermaier and the non-slide into second base

Let’s slide into the math.

MLB: Tampa Bay Rays at Atlanta Braves Adam Hagy-USA TODAY Sports

During last night’s game against the Braves in Atlanta, Rays manager Kevin Cash did something a little out of the ordinary: down one run, he swapped in a pinch runner for the man on first base, bringing in Kevin Kiermaier to run for the not-that-slow Brandon Lowe.

There was already one out, as left fielder Adam Duvall had made an astounding dive at the warning track to rob Jose Martinez of a no-doubt double. If that ball wasn’t caught, you might have expected a pinch runner to be the man on second for Brandon Lowe at the plate, but alas, when Lowe singled there was no one to run home.

Kiermaier taking first base here was an old-school move from a new-school manager, and gave Rays fans an odd feeling. Kevin Kiermaier is here to do exactly one thing: try and steal second base.

With the formidable Hunter Renfroe at the plate, Kiermaier — who had 19 steals last season — got a perfect jump at the start of the at bat and would have been safe on a slide into second base easily, had Renfroe not fouled off the pitch.

Kiermaier returned to first base, took his lead off the bag yet again, and what did Braves pitcher Mark Melancon do? Fire a fastball as hard as he could to catcher Tyler Flowers, who received the ball already in a standing position.

It was essentially a pitch out, but was indeed inside the zone.

At this point, everyone and their mother knows Kevin Kiermaier was about to attempt to steal second base, particularly after the attempt the previous pitch. Was it wise to be trying it again? Or was the design not a steal, but a hit-and-run? And if that were the case, why didn’t Renfroe swing at the pitch inside the zone?

Nevertheless, Kiermaier took off running again, Flowers received the pitch standing up, and KK made a baffling mistake: He didn’t slide.

You can watch the full sequence of events here:

After the game, Kiermaier explained that he didn’t slide because he thought he was going to have to return to first base again:

The only explanation for this — given the low level of noise in the stadium — is that Melancon’s fastball to Flowers was caught in such a way that the catcher’s mitt rang out.

You know the feeling? When you’re playing catch and the other person fires a fastball your way? If you catch it a certain way, the mitt will be loud enough to give you pause (you might even need to pause to shake your hand out). Maybe that was the mitt of Flowers.

As for what Kevin Kiermaier must be feeling, given his singular responsibility for the out, it’s pretty relatable to another sport: football.

There are moments on the field where a player gives up on a play in football because they thought they heard the whistle from the ref, particularly when a fumbled ball is bouncing on the turf. The player will stand there or jog away as a player from the other team picks up the live ball and runs off. It’s not a play that decides the game, but it sure could have made the difference.

And when games are worth triple their normal weight in a shortened season that might only get shorter? Yeah, that out could have made a world of difference.

As for Kevin Cash, after the game, he seemed to assume Kiermaier got caught in between steps on when he would have started his slide,

“from the looks of it, all I care about is that he didn’t hurt himself.”

As a parting thought: if your upside from a player making a game-killing mistake is that he was avoiding injury, perhaps that’s not right player to swap in as a base-runner, particularly when that player already has a history of incurring injuries...

As for whether KK should have had the green light at all, that’s a question of the run expectancy and success rates.

Math is a sliding scale

Using the slightly out of date run expectancy matrix in the FanGraphs glossary, we can find the following “expected runs” per event:

  • With a man on first and one out (the starting position): 0.489 expected runs
  • With a man on second and one out (if Kiermaier would have stolen successfully): 0.644 expected runs
  • With no one on base and two outs (after Kiermaier was thrown out): .095 expected runs

There are some ancillary cases in there (like if the ball is thrown into center field, or if Hunter Renfroe would have hit a single while Kiermaier was stealing), but ignoring them we get an increase of .155 runs with a successful execution, and a loss of .394 runs on a failure. That works out to a break even point of around 72%, meaning that, if Cash thinks that Kiermaier has greater than a 72% chance of stealing second base, he should send him.

Well, Kiermaier has stolen 90 bases in his career, while being thrown out 29 times, for a success rate over 75%. That means it was a good decision, right?


Kiermaier has never stolen more than 21 bases in a season, meaning that he’s not really a volume stealer. There’s a difference between stealing a base when you notice that the pitcher isn’t really paying attention and you’re able to time him up well than when you’re there to steal second and everybody in the stadium knows it. That should nudge the expected success rate down from 75%.

Then you have the fact that Melancon is a tough right handed pitcher, with a legacy of finishing games in high leverage situations, that neither Renfroe or Adames should be expected to have easy luck against at the plate. This lowers the overall run environment as well, but also raises the relative value of a successful steal, because an extra-base hit, or two consecutive singles, become more unlikely. That would mean that Cash could logically give the green light at a lower expected success probability than that average of 72% given his expected probability at the plate.

I bet you can come up with other reasons to slide this break-even point one way or the other. Bottom line, though, it’s close.

Unlike the play at second.