When an injured pitcher makes his first start after a rehab assignment, he doesn’t usually throw a lot of pitches. When a pitcher hasn’t started in a couple of weeks, he doesn’t usually throw a lot of pitches. When a pitcher who has been working out of the bullpen most the year makes a start, he doesn’t usually throw a lot of pitches. This is common sense, and yet betting markets don’t seem to realize this -- at least not to the fullest extent.
The Rays’ Drew Rasmussen threw 71 pitches against the Boston Red Sox on Sept. 7 and struck out two batters. A no-name pitcher with a run-of-the-mill stat line wouldn’t normally be noteworthy, except that betting markets set his strikeout prop at 5.5 with an implied projection (after accounting for juice) of 5.16. My projection system, THE BAT X, projected just 2.49 strikeouts for Rasmussen. After all, he has been a reliever most of the year and has been kept to 60 or so pitches in most of his “starts.” Yet betting markets thought he’d strike out double his most likely outcome. This was one of the most egregiously inefficient strikeout props I’ve ever seen and is a perfect example of one type of edge that can be found for betting strikeout props.
Props can be inefficient for any number of reasons, but not accounting for expected pitch volume is easily exploitable for anybody who pays attention to this sort of thing or who has access to THE BAT X, which gives users projected max pitches for every pitcher every day. It doesn’t matter if Freddy Peralta normally strikes out seven batters per start. If he’s going to throw only 70 or 80 pitches, as was the expectation Sept. 8, he likely won’t reach seven strikeouts. He went 3.2 innings and struck out four that day. Even the matchup has to be considered a secondary factor for these types of pitchers. It doesn’t matter how much the opposing lineup strikes out if the pitcher doesn’t go deep enough to exploit it.
To roughly test this, I (with the help of EV Analytics, which ran the market data for me) looked at all pitchers who projected via THE BAT X with a max pitch count under 80 in any start this season. This has happened 95 times — or about once every couple of days, on average. Without even looking at THE BAT X’s actual projection (which will account for plenty of additional factors and will give us a further additional edge), if you were to just blindly bet the Under on these pitchers, you would have hit on 59% of your bets with an ROI of about 4.5%. And this is comparing to closing lines, which are going to be much sharper than if you were to have hit these lines earlier in the day before bettors who pay attention to pitch limits have the chance to move the lines.
In other words, if you knew literally nothing else except that a pitcher was likely to have a pitch limit and you bet the Under on his strikeout prop every time, you would have turned a noteworthy profit over the course of the 2021 season. Betting is about finding edges, and this is one worth paying attention to.
On Wednesday, we will likely have three pitchers who will meet our criteria: Merrill Kelly, Alex Cobb and Scott Kazmir. I don’t know what their K prop lines will be yet, but it seems likely they’ll be too high.