Chalk of the Day, August 21: Ohtani to homer at +215

The chalkiest home run prop on the Friday board, checked against 5,000 play-by-play simulations of the Pirates at the Dodgers. The +215 price implies 31.7%. The simulations say 26.3%. Negative EV at about -17%; it becomes a play at +280 or longer.

Written by Jesse, NegativeEV. Last updated 21 August 2026.

• Sample: 5,000 pitch-by-pitch simulations of one game
• Window: 21 August 2026 slate
• Priced at: +215 at Bovada, as quoted off the board at publication
• Measured: 2026-08-21

The bet

The check:

This is the most-bet home run prop on Friday's board, and the simulations disagree with the price on it. 13 games had odds, 17 of the chalkiest selections were graded against the sims, and the verdicts came back 15 Negative EV, 0 Roughly Fair, 2 Positive EV. Nobody here is picking anything. This is a price the public is already taking, checked.

The board ran from +200 to +225 on this prop across 5 books at the time of the check. Every one of those prices is short of +280, so where you shop changes how much this costs you, not whether it costs you.

This prop is quoted over-only, so there is no two-sided market to strip the book's rake out of. The honest comparison is the simulated number against what the quoted price implies, and some of that gap is the rake itself.

What the simulations did

Across 5,000 simulations Ohtani's average is 0.29 home runs and the median is 0. The most common outcome by a distance is none at all.

The shape of 5,000 simulations:

The anytime line pays the same for all of the multi-homer games, and there are 3.0 in every 100 of them.

At 5,000 simulations that 26.3% carries a standard error of 0.62 points, so 95 runs in 100 would land between 25.1% and 27.5%. The gap to the price is about 5 points, roughly 9 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

Ohtani bats on the home side, which cuts the other way here: his last trip only happens if the game needs a bottom of the ninth, and it does not always need one. Across the runs 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:

Pooled across every simulation he goes deep on 6.6% of his trips, so whether he bats one more time or one fewer is worth more here than any read on his swing. That extra trip is not his to take either. It depends on the eight hitters around him keeping the order moving, and in the simulations they do not always do it.

What works for him

• His own career profile, who he is as a hitter, props the number up by about 8.7 points. Neutralize it and 26.3% becomes 17.6%. HR rate .087, 5 of 308 hitters, top 10%. BABIP .328, 28 of 308 hitters, top 10%. K rate .246, 200 of 308 hitters, middle of the pack. Exit velo 94.3, 3 of 308 hitters, top 10%. Launch angle 14, 186 of 308 hitters.

What works against him

Three arms clear their own noise on this side, and together they are the story.

• Bubba Chandler's career profile, the pitcher he faces, takes about 4.1 points off. Neutralize it and 26.3% becomes 30.4%. HR rate .018, 29 of 262 pitchers, top quarter. K rate .216 against .207 on the season, 165 of 262 pitchers, middle of the pack. Hits allowed per batter faced .198 against .197 on the season, 60 of 262 pitchers, top quarter. Walk rate .119 against .135 on the season, 231 of 262 pitchers, bottom quarter. Fastball 98.5, 260 of 262 pitchers.
• His own recent form takes about 2.5 points off. Neutralize it and 26.3% becomes 28.8%. HR rate .080 against .081 on the season, .087 for his career, 14 of 308 hitters, top 10%. BABIP .340 against .324 on the season, .328 for his career, 15 of 308 hitters, top 10%. K rate .250 against .237 on the season, .246 for his career, 117 of 308 hitters, middle of the pack. Exit velo 93.2 against 93.5 on the season, 94.3 for his career, 12 of 308 hitters, top 10%. Launch angle 8.8 against 13 on the season, 14 for his career, 133 of 308 hitters.
• Playing at home takes about 1.2 points off. Neutralize it and 26.3% becomes 27.5%. His last trip only happens if the game needs a bottom of the ninth, and it does not always need one.

The pitcher

A right-hander, 1,900 pitches into the season and ranked against the 568 pitchers with enough of them to compare. He releases from a three-quarters slot, 5.54 feet up (40th percentile) and 1.07 feet across (15th), with 6.64 feet of extension (70th percentile).

The ballpark

UNIQLO Field at Dodger Stadium ranks 14th of 30 for home runs, with a park factor of 1.07 where 1.00 is neutral. It is middle of the pack. In the 2026 data home runs land on 5.1 of every 100 balls in play in the Dodgers' home games against 4.7 in their road games, 2,754 batted balls at home, 2,718 away, the same club on both sides of the split, so what is left is the park. Open roof, grass, 330 feet to left, 395 to centre, 330 to right, 515 feet of elevation. Tonight it is 79 degrees with a 5 mph wind blowing out to right.

Shohei Ohtani, recent against season:

• usual lineup spot: 1st (over 115 games)
• plate appearances this season: 510
• plate appearances in the recent window: 20

Those are the inputs the simulator was served, not a separate stat source.

The rest of his night

The home run does not arrive alone. Split across the 5,000 simulations on whether it lands:

:

The game itself averages 7.94 total runs. His side scores 5.67 when the homer lands against 3.90 when it does not, so this is not an isolated event - it travels with the whole offence.

What this does and does not say

It says that at +215 the price is asking for more than the simulations produce. It does not say he will not homer. He goes deep in 26 of every 100 simulated games. Every play is relative to its price, and the two numbers meet at +280.

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. 13 of the 37 came back with a direction we can stand behind. The price is +215 as quoted at Bovada at publication, and the check is against that quoted price, rake included.

Inside the noise floor

24 of the 37 arms sit inside their own noise, including the rest of the order, the other eight, without him (+1.1), Bubba Chandler's season form (+0.6), his own season form (+0.2), the weather (-2.3), the ballpark (-1.0), what Bubba Chandler has been throwing lately, his pitch mix (-0.6), how long Bubba Chandler stays in (-0.2). 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 can be named the thing driving this.

Written up for readers: https://negativeev.com/about/home-run-props All findings: https://negativeev.com/research