In the year 2000, there were 75 different pitchers who made at least 10 starts in which they were allowed to throw at least 105 pitches. By 2019, that number had plummeted all the way to just 13 hurlers. Between teams being far more attentive to how they handle the workload of their staffs along with the development of "super bullpens" with inning-specific specialists being used over the final third of most games, seeing starting pitchers work for more than six innings is becoming more and more of a rarity.
Protecting the arms of aces (both current and potential) is the way of the baseball world these days. In an attempt to prevent injuries (or a recurrence of a previous injury) due to overuse, innings caps and pitch counts have become commonplace. And, in terms of fantasy baseball, heading into drafts, managers have often taken long looks at the previous season's starting pitcher workloads to try and identify pitchers who might have been "overworked." Those are the mound residents who could well be in line for, at best, being saddled with restrictions for the upcoming season and, at worst, potential serious injury.
A National example
Let's take a look at the case of Washington's Stephen Strasburg. In 2019, Strasburg threw 3,384 pitches in the regular season -- a career-high -- and then added 559 more pitches over six post-season appearances for good measure. Given Strasburg's history of injuries, this extreme amount of work was a thunderous klaxon that perhaps 2020 would be a problem. And, in fact, even with the shortened season and late start, it didn't take long for "carpal tunnel neuritis of the right hand" to flare up, with surgery eventually ending Strasburg's year.
While the connection between the 2019 pitch total and the 2020 injury might not necessarily be a straight line, it probably didn't surprise anyone either. Fantasy managers who had hedged against drafting Strasburg due to the mere potential of this happenstance certainly were glad that they had read the tea leaves correctly here. Similarly, nobody was too stunned to see Justin Verlander need Tommy John surgery after an age-37 season where he threw 4,046 pitches.
There's a common-sense radar that kicks in when there's an unusually large season-over-season increase in either innings or pitch count. It's an omen that too often bears unfortunate fruit. Similarly, when a pitcher survives a season without any trips to the IL and his workload doesn't vary all that much from previous years (or perhaps even goes down a bit), there's a tendency for fantasy managers to believe that there's less risk of arm troubles up ahead. And there's nothing wrong with these feelings.
However, after a 2020 season that consisted of only 60 games, there seems to be a general sense that there shouldn't be any concern at all headed into 2021. After all, how much of a problem could there be for pitchers used to throwing 150-200 innings a year following a season where they ended up throwing in only the 60-80 inning range? Well, I believe there may be some warning signs to be noticed, even after an unprecedentedly short schedule.
Counting pitches properly
Sabermetrics legend Tom Tango has done a lot of work with estimated pitch counts, including a ton of research into figuring out the expected number of pitches a pitcher "should have thrown," based on their innings pitched, strikeouts, walks and hits allowed. It stands to reason that if we have a solid formula for predicting the expected number of pitches based on actual game outcomes -- which Tango's work does provide us -- then any variance between that number and the actual pitch count is likely the result of a pitcher working harder than he needs to.
More to the point, many starters have innings and full outings in which they work too hard compared to what they "should have" done. Over the course of a full season, you'd expect those games to be somewhat balanced by those where they cruise in terms of pitch count to the expected workload, given the outcome.
Where red flags should definitely be raised for fantasy managers is if a pitcher is consistently throwing "too many pitches." Over the course of the season, those extra pitches tend to add up and result in tired arms over the latter parts of the campaign - even in a "truncated due to a pandemic" season - and the impact of that could indeed linger into the following season, resulting in a higher risk for things like lost velocity, a tired arm come September, or the worst-case scenario; a serious injury.
Let's look back at Mr. Strasburg for a moment. In 2019, his pitch count when compared to Tango's target number (which I'm calling his Work Number) was plus-104.5 (including the playoffs). Compare that to 2014, when he was able to get through the entire season and throw a career-high 215 innings. His Work Number that year was minus-86.4, the least stressful (by far) season of his career. So, even though we probably shouldn't have been concerned headed into 2015, he actually ended up with a Work Number of plus-27.4. That huge increase in stressful outings most certainly contributed to his two IL stints that season.
What to do with the Work Number
I would argue that we can use Work Number in the following ways to help minimize the risk of drafting pitchers destined for the IL.
Pitchers who have a high (plus) Work Number during a given season are more at risk to get injured during that season. Obviously, this isn't going to help you on Draft Day, but it is something you can track say, come May, and we begin to get a sense of how things are going for each individual pitcher.
Pitchers who had a very low (minus) Work Number for a given season are less at risk for serious injury the following year. This can be a tie-breaker between two pitchers of relatively equal ability on Draft Day, but there's a caveat attached to this. As we saw in the case of Strasburg, if a starter begins to accumulate a much higher Work Number during a given season compared to the previous year -- even one that may have been less taxing than expected -- you may want to consider "trading high" just in case those extra pitches do indeed start to add up and lead your fantasy ace closer to the IL.
Pitchers who had a very high (plus) Work Number for a given season are more at risk to get injured early the following season - and that risk only increases if that Work Number remains high going forward. I'm not saying you don't draft Gerrit Cole just because his Work Number from last season was plus-70.9. But if his 2021 Work Number is at around plus-50 after 6-7 starts? I'm definitely seeing what the market has to offer. However, if we get to early May and his Work Number is plus-20 or lower? In that case, I'm going to feel pretty confident that he's survived any potential "overwork hangover" from the previous season.