The Importance of Selecting an Opening Day Starter

WARNING: The following post is nerdy. Stats and stuff.

With the MLB lockout souring most baseball-related news and pausing the hot stove league, Opening Day 2022 might seem even further away than it appears on the calendar.  To that end, perhaps it’s a worthwhile exercise to skip ahead of the murkiness of the current offseason and simply talk about the importance of Opening Day.  Generally speaking, Opening Day is little beyond the fanfare in celebration of initiating a new season; it’s one game in the least dramatic part of the season – not quite the first sixth of a mile in a full marathon.  And when managers name their Opening Day starters, its worn like a badge of honor.  But why?  Anyone could start Opening Day and it shouldn’t alter projected standings by any noticeable amount.  And Opening Day carries no more value in the standings than the second game of the year, or the third, or the eighth, or the forty-seventh, or the…you get the point.  The argument in favor of aligning your top pitchers with your opponents’ top pitchers can be picked apart when you consider the effect of having your top pitchers lined up with your opponents’ worst.  By and large, it would seem there isn’t – or perhaps shouldn’t be anything to naming your Opening Day starter other than to honor a pitcher on the most exciting day in baseball since the last out of the World Series…

Or is there more to it?

End of Season IP, GS, and xFIP Rank of Opening Day Starting Pitchers

Occasionally we’ll see a manager who seemingly “rewards” a starting pitcher with the Opening Day nod in spite of the availability of more talented options on his team’s starting staff.  More often than not, these cases are spurred by fans, and any disparity in talent that exists between the pitcher getting the nod and the alternative(s) can be ostensibly vague.  An example: German Marquez probably should’ve gotten the Rockies 2019 Opening Day start over Kyle Freeland given his 3.10 xFIP versus Freeland’s 4.22 in 2018.  But Freeland also collected an equivalent WAR total to Marquez and posted a lower ERA – though xFIP is a much better indicator of future ERA than both ERA and FIP.  The point is, while there was an argument to be made for Marquez, both pitchers’ were equally productive in the season prior, which is often the most significant body of work managers (among others) are paying attention to when determining their man on Opening Day, as well as the upcoming season. 

But what exactly is set into motion when a manager names an Opening Day Starter?

Here’s where my 2019 Rockies example gets about as interesting as one could expect a 2019 Rockies anecdote to get.  Unfortunately for Kyle Freeland, he regressed much more significantly in 2019 than could even have been expected given the differential between his ERA and xFIP in 2018.  He ended up making just 22 starts due to multiple IL stints, but his season was a disaster from the beginning. But in spite of the disaster, he was still tied with Marquez for the team lead in Games Started at the end of May before hitting the IL for the first time.  But why did Freeland keep getting the nod so consistently for the first two months?  Why had he started more games than everyone but Marquez to that point? 

(A part of) the answer?  Because Freeland was the starting pitcher on Opening Day.

Not only did an argument exist for Marquez over Freeland on Opening Day 2019, but so too did an argument for Jon Gray to be in front of Freeland in the Rockies’ rotation (Gray, despite what appeared to be an awful 2018, still posted a 3.47 xFIP – also better than Freeland’s the prior year).  Not only does an Opening Day Starter come first in the rotation, the title itself garners attention from both fans and media; Opening Day Starters are, at the very least, nominal aces.  Given their status within a rotation, it’s generally difficult to skip your Opening Day starter without raising eyebrows. 

I’m not saying that naming a different Opening Day Starter would’ve made the 2019 Rockies a good or even average team – it wouldn’t have.  What I’m getting at is, in naming an Opening Day Starter, a manager is effectively electing the pitcher he wants to pitch more innings than anyone else by season’s end (among the team’s pool of healthy pitching options on Opening Day).  The data supports this idea too.  Opening Day Starters are more likely to finish first on their staff in IP than they are any other individual rank; they’re over twice as likely to finish first than they are to finish second.

While a pitcher’s performance isn’t something a manager can control, and a pitcher’s innings is something a manager can, it’s still worth noting that the rate at which Opening Day Starters end up being their team’s best-performing SP is much less frequent than the rate at which they end up the team’s innings leader (we’re quantifying performance using xFIP).  Historically speaking, Opening Day Starters are more likely (albeit only slightly at 52%) to finish their season with an xFIP that ranks third or worse on their team’s starting staff.  At the same time, they’re still very likely (61%) to finish first or second on their staff in Innings Pitched (full disclosure – Opening Day Starters finish 3rd or worse AND in the top 2 in IP on their respective staffs about 27% of the time).

Sure, Opening Day is just one game in the standings with no more face value than a game played on any other date in the regular season.  But it’s also a strong predictor of who will carry the biggest workload on a staff, and that makes Opening Day a statistically important date (not just a nominally important one).  Talent aside, your Opening Day starter is your most probable workhorse by season’s end.  Factors like injuries, innings limits, service time manipulation, player options, and roster constraints can all play a role in a manager’s decision to name an Opening Day Starter who isn’t the most talented starting pitcher available to him.  But the fact remains that whoever starts the first game of the year is probably going to take on a bigger workload than anyone else who pitches over the course of the season.

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