Chalk of the Day, August 17: Ohtani to homer at +180

The chalkiest home run prop on the Monday board, checked against 5,000 play-by-play simulations of the Dodgers at the Rockies. The +180 price implies 35.7%. The simulations say 38.9%. Positive EV at about +9%; it stays a play down to +157.

Written by Jesse, NegativeEV. Last updated 17 August 2026.

• Sample: 5,000 pitch-by-pitch simulations of one game
• Window: 17 August 2026 slate
• Priced at: +180 at Bovada, as quoted off the board at publication
• Measured: 2026-08-17

The bet

The check:

This is the most-bet home run prop on Monday's board, and the simulations make it better than the price on offer. 9 games had odds, 18 of the chalkiest selections were graded against the sims, and the verdicts came back 12 Negative EV, 0 Roughly Fair, 6 Positive EV. Nobody here is picking anything. This is a price the public is already taking, checked.

The board ran from +170 to +200 on this prop across 6 books at the time of the check, against the +157 this needs to break even.

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 0.48 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 8.0 in every 100 of them.

At 5,000 simulations that 38.9% carries a standard error of 0.69 points, so 95 runs in 100 would land between 37.5% and 40.2%. The gap to the price is about 3 points, roughly 5 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 away side, which is the cleanest thing working for him: he is guaranteed all nine innings, and there is no scenario where his side is up after eight and he loses a turn. Across the runs he comes up 5.24 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 9.1% 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

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

• His own career profile, who he is as a hitter, props the number up by about 8.2 points. Neutralize it and 38.9% becomes 30.7%. HR rate .086, 6 of 304 hitters, top 10%. BABIP .328, 28 of 304 hitters, top 10%. K rate .247, 200 of 304 hitters, middle of the pack. Exit velo 94.3, 3 of 304 hitters, top 10%. Launch angle 14.1, 186 of 304 hitters.
• The weather props the number up by about 2.3 points. Neutralize it and 38.9% becomes 36.5%. That arm neutralizes temperature, wind and conditions at once, so the cause is not separable. It is 91 degrees with a 6 mph wind blowing right to left.
• Playing on the road props the number up by about 1.2 points. Neutralize it and 38.9% becomes 37.6%. He is guaranteed all nine innings, whatever the score after eight.

What works against him

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

• Tomoyuki Sugano's season form takes about 2.5 points off. Neutralize it and 38.9% becomes 41.4%. HR rate .053 against .052 for his career, 245 of 247 pitchers, bottom 10%. K rate .136 against .150 for his career, 244 of 247 pitchers, bottom 10%. Hits allowed per batter faced .249 against .255 for his career, 229 of 247 pitchers, bottom 10%. Walk rate .056 against .059 for his career, 10 of 247 pitchers, top 10%. Flyballs .216, 213 of 247 pitchers, bottom quarter. Groundballs .248, 45 of 247 pitchers, top quarter.
• His own recent form takes about 2.5 points off. Neutralize it and 38.9% becomes 41.3%. HR rate .070 against .078 on the season, .086 for his career, 26 of 304 hitters, top 10%. BABIP .380 against .327 on the season, .328 for his career, 17 of 304 hitters, top 10%. K rate .350 against .240 on the season, .247 for his career, 255 of 304 hitters, bottom quarter. Exit velo 95.4 against 93.4 on the season, 94.3 for his career, 23 of 304 hitters, top 10%. Launch angle 16.6 against 13.3 on the season, 14.1 for his career, 170 of 304 hitters.

The pitcher

A right-hander, 1,715 pitches into the season and ranked against the 561 pitchers with enough of them to compare. He releases from a three-quarters slot, 5.8 feet up (65th percentile) and 2.34 feet across (80th), with 6.22 feet of extension (28th percentile).

The ballpark

Coors Field ranks 12th of 30 for home runs, with a park factor of 1.10 where 1.00 is neutral. It is middle of the pack. In the 2026 data home runs land on 4.9 of every 100 balls in play in the Rockies' home games against 4.4 in their road games, 3,093 batted balls at home, 2,873 away, the same club on both sides of the split, so what is left is the park. Open roof, grass, 347 feet to left, 415 to centre, 350 to right, 5190 feet of elevation. Tonight it is 91 degrees with a 6 mph wind blowing right to left.

Shohei Ohtani, recent against season:

• usual lineup spot: 1st (over 112 games)
• plate appearances this season: 495
• 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 12.89 total runs. His side scores 9.63 when the homer lands against 7.41 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 +180 the price is asking for less than the simulations produce. It does not say he will homer. He does not in 61 of every 100 simulated games, which is what a price this long is quoting in the first place. Every play is relative to its price, and the two numbers meet at +157.

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. 14 of the 37 came back with a direction we can stand behind. The price is +180 as quoted at Bovada at publication, and the check is against that quoted price, rake included.

Inside the noise floor

23 of the 37 arms sit inside their own noise, including the rest of the order, the other eight, without him (+1.3), what Tomoyuki Sugano has been throwing lately, his pitch mix (+1.0), how long Tomoyuki Sugano stays in (+0.2), his own season form (-1.9), Tomoyuki Sugano's career profile, the pitcher he faces (-1.5), the ballpark (-0.7). 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