Chalk of the Day, August 12: Murakami to homer at +270

The chalkiest home run prop on the Wednesday board, checked against 5,000 play-by-play simulations of Cincinnati at the White Sox. The +270 price implies 27.0%. The simulations say 19.3%. Negative EV at about -28%; it becomes a play at +417 or longer.

Written by Jesse, NegativeEV. Last updated 12 August 2026.

Watch: https://youtube.com/watch?v=a2uGydOpwNE

• Sample: 5,000 pitch-by-pitch simulations of one game
• Window: 12 August 2026 slate
• Priced at: +270, as quoted off the board at publication
• Measured: 2026-08-12

Narration on the episode is synthetic, voiced from the written read; the analysis is the simulator's.

The bet

:

This is the most-bet home run prop on Wednesday's board, and the simulations disagree with the price on it. Fifteen games had odds, 21 of the chalkiest selections were graded against the sims, and the verdicts came back 19 Negative EV, 2 Roughly Fair, 0 Positive EV. Nobody here is picking anything. This is a price the public is already taking, checked.

What the simulations did

Across 5,000 simulations Murakami's average is 0.21 home runs and the median is zero. The most common outcome by a distance is none at all.

The shape of 5,000 simulations:

At 5,000 simulations that 19.3% carries a standard error of 0.56 points, so 95 runs in 100 would land between 18.2% and 20.4%. The gap to the price is roughly 14 times that error bar. Said narrowly, and it should be said narrowly: that means only that re-running the simulator would not move the number far enough to reach the price. It is not a claim that we are right and the book is wrong. A number that is systematically off is off to as many standard errors as you like.

How many cracks he gets

This is the concrete argument of the day. Murakami bats on the home side, so his last trip to the plate only happens if the game needs a bottom of the ninth. Across the simulations he comes up 4.46 times on average, at-bats plus walks, and the home run number moves with that count.

Trips to the plate, and what each one is worth:

Six trips is roughly where the price is already set. Six trips happens 3 times in 100. Pooled across every simulation he goes deep on 4.7% of his trips, so whether he bats a fourth or a fifth time is worth more here than any read on his swing. That extra inning is not his to take either. It depends on the eight hitters around him keeping the ninth alive.

What works for him

Quite a lot, which is what makes this a price story rather than a bad-hitter story. Every figure below sits inside its own arm's noise, so treat each as a measurement and not a verdict. None of them can be called the thing driving the number.

• His own career profile as a hitter is worth about 1.8 points. Over his last 20 trips to the plate his home run rate ranks 10th of 295 hitters, the top 10% of the league. This is a real power bat.
• His season form adds about 1.7 points. Same shape, same story: 26 home runs in 357 plate appearances over 83 games, at a 94.2 mph average exit velocity.
• The ballpark is worth about 1.8 points, which is the surprise of the day once you see what the park actually is.
• The weather is worth about 0.4 points. 76 degrees, wind 4 mph, blowing out to right field.

The ballpark

Rate Field ranks 24th of 30 for home runs with a park factor of 0.82, where 1.00 is neutral. It is one of the harder places in the league to hit one. Home runs land on 4.3 of every 100 balls in play in the White Sox's home games against 5.3 in their road games, same club on both sides, across 2,793 batted balls at home and 2,676 away this season. Open roof, grass, 330 feet to left, 400 to centre, 335 to right, 595 feet of elevation.

So a venue arm that measured 1.8 points in this hitter's favour is not something to wave through. It is inside the noise, and there is no clean explanation for it on hand. It is printed here because everything is printed, not because it has been understood.

The pitcher

Rhett Lowder, and Murakami has never faced him: zero career plate appearances. Lowder is a right-hander, 1,508 pitches into the season and ranked against the 550 pitchers with 200 or more. He throws from a three-quarters slot, 5.48 feet up (34th percentile) and 2.2 feet across (75th percentile), with 6.16 feet of extension (23rd percentile). Neither of the two arms about him separates from the noise: his career profile measured 1.1 points in Murakami's favour, his season form 0.1.

What works against him

Less than the price implies, and again nothing that clears its own noise floor.

• His own recent form takes about 1.8 points off. Over his last 20 plate appearances he is striking out 40% of the time against 34.3% on the season. That recent strikeout rate ranks 269th of 295 hitters, the bottom 10% of the league.
• Batting at home costs about 0.3 points. That is the ninth-inning problem above, priced.
• How long Lowder stays in is worth about 0.0 points, which is to say nothing the simulator could measure.

Murakami, recent against season:

He usually bats second, and 20 plate appearances is a fortnight, not a trend. The strikeout column is the one worth keeping in the back of your mind.

What this does and does not say

It says that at +270 the price is asking for a version of this game in which he gets six trips to the plate, in a park that suppresses home runs, at a strikeout rate that has been rising over his last 20 times up.

It does not say he will not homer. He homers in 19 of every 100 simulated games, which is a lot. It is simply not 27 of them. The two numbers meet at +417.

One prop is one game, and one game is mostly variance. The reason to run 5,000 of them is to find out what the price would have to be before the bet made sense, not to call the evening.

Method

The game is simulated pitch by pitch 5,000 times from the projected lineups, and the prop is graded on how often it lands. 37 factors were neutralized one at a time, each arm a separate 4,000-simulation re-run, so one-at-a-time swings do not sum to the projection. Those 37 cover everything that could bear on this hitter rather than every factor in the game: the other hitters' own career, season and recent tiers were skipped on purpose, because they are most of the cost and none of the answer for a prop about one man. 6 of the 37 came back with a direction we can stand behind, and not one of the six is about Murakami. The price is +270 as quoted off the board at publication, and the check is against that quoted price, rake included. This prop is quoted over-only, so there is no two-sided market to strip the book's rake out of, and some of the gap is the rake itself.

Inside the noise floor

31 of the 37 arms sit inside their own noise, and every arm about Murakami is one of them: his career profile (1.8 points), the ballpark (1.8), his recent form (1.8), his season form (1.7), the rest of the order without him (1.3), Lowder's career profile (1.1), the weather (0.4), batting at home (0.3), Lowder's season form (0.1) and how long Lowder stays in (0.0). Those numbers are real measurements and they are printed rather than dropped, but at this simulation count the arm cannot tell a small real effect from no effect. So none of them does nothing, and none of them is what is driving this. The price is what is driving this.

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