Handicapping Mariners-Athletics on Opening Day in Japan

From a handicapping perspective, having the first two games of the Major League Baseball season played at a neutral site eliminates a lot of the factors that would normally need to be considered when betting on baseball. Home field advantage, travel, and rest can all be removed from the equation.

From a domestic marketing perspective, it seems a bit strange that the first pitch of the baseball season will occur between two AL West teams playing on a Wednesday … in Japan … before it's dawn on the East coast … the day prior to the men's NCAA tournament.

So while everyone else is focused on filling out their brackets, we can get a jump on finding some edges in the baseball market.

A Quick and Rough Calculation for Pitcher Adjustments

When handicapping baseball, the most important adjustment that you will need to make on a day-to-day basis is to consider the relative quality of the projected starting pitchers (or projected daily staff, thanks to Tampa Bay) for each team.

One quick way to determine this is to use xwOBA (expected weighted on-base average), as provided by Statcast metrics through Baseball Savant.

If you play daily fantasy baseball, you might be familiar with wOBA. If not, all that you need to know is that wOBA is a weighted statistic meant to measure a player's contributions per plate appearance. For a pitcher, wOBA measures the expected contributions against them.

More importantly, wOBA and xwOBA can be converted into runs per nine innings, by following these steps: 1) divide the player wOBA by the league average wOBA (.315 in 2018); 2) Square that sum (multiply that number by itself); and 3) Multiply the sum from Step 2 by the league average runs per game (4.53 over the past three seasons).

Adjusting Pitchers for 5 Inning Lines

Per Statcast, Mariners starting pitcher Marco Gonzales has an xwOBA of .308, while Athletics starting pitcher Mike Fiers owns an xwOBA of .333. By following the steps in the paragraph above, those figures translate to a 4.30 earned run average (ERA) for Gonzales and a 5.03 ERA for Fiers.

Starting pitchers don't pitch the whole game, however, unless they are completely dominating (but in 2019, even that is no guarantee). The best quick way to use xwOBA for most pitchers, then, is to assume that they will pitch the first five innings of the game.

In 2018, MLB teams averaged 2.5 runs scored, per team, over the first five innings of all games. This accounted for 56% of all runs scored. As a result, the simple adjustment for five inning lines is to multiply the ERA (as converted from xwOBA) by 0.56.

That should give you the projected average pitcher output, over a five-inning sample, and you can adjust downwards or upwards depending on the opposing lineup wOBA.

For full-game projections, you can multiply a composite bullpen ERA (converted from their wOBA) by 0.44, and make a similar adjustment based upon the opposing lineup wOBA. Add that together with the projected five-inning line, and you have your projected full game line.

Mariners-Athletics: MLB Season Opener Odds, Analysis

By this point, you must be saying, "OK, enough with the math, guy. Can you just tell me your projections so that I can place a wager on a game that I will likely sleep through?"

Fair enough. Here's what I'm seeing for the first tilt of the season:

First Five Innings

• Projected Score: Mariners 2.61 | A's 2.51
• Current Line:  Mariners (+108) | A's (-130)
• Projected Total: 5.12
• Current Over/Under: 4.5 (o-120)

There are two small edges in the first five innings of the game.

The current odds on the over sit at -120, but the model projects the fair odds at -129, with an edge of 1.89% at the time of writing. I would consider the Over 4.5 at -115.

The actionable edge is on the Mariners moneyline at plus odds, as the superior A's lineup is not projected to overcome the discrepancy between Gonzales and Fiers.

The model suggests a true edge of 3.4% on the Mariners five-inning moneyline at +110 (fair odds -104). I'd play it down to +105.

Full Game

• Projected Score: Mariners 4.45 | A's 4.54
• Current Line:  Mariners (+120) | A's (-130)
• Projected Total: 8.98
• Current Over/Under: 8.5

The model expects the A's to ultimately win the game due to the quality of their bullpen, but also sees this contest as a relative coinflip overall.

At fair odds of +102, there is a small edge (4%) on the Mariners full game moneyline — but I'd much rather play them in the first five innings and avoid the potential for blown saves with Edwin Diaz no longer walking through that bullpen door.