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Rookie Pitcher Impact in Diamondbacks History

Brandon Webb pitches Photo by Stephen Dunn/Getty Images

On Tuesday Jim recapped some of the best single game pitching debuts in Diamondbacks franchise history. Coincidentally, the excitement over the outings from Merrill Kelly and Jon Duplantier got me thinking about the possible usage of rookie pitchers for the team in 2019.

There are 9 pitchers on the 40 man roster with Rookie Status still intact, including Jon Duplantier, Merrill Kelly, Yoan Lopez, Taylor Clarke, Joey Krehbiel, Joel Payamps, Jimmie Sherfy, Bo Takahashi, & Emilio Vargas. In addition, Taylor Widener is a good bet to be added to the 40 man and the active roster at some point. It would seem there is a very good chance we could see significant innings being pitched by the rookies on the roster this year, even if the team is not a seller at the trade deadline.

That being the case, I decided to look at franchise history and see which seasons had the most games and innings pitched by pitchers who still had rookie status. A Note on Rookie Status first though: Players are often rookie eligible in more than one season.

To qualify as a rookie in Major League Baseball, a player must not have exceeded 130 at bats or fifty innings pitched in the majors, and also fewer than 45 days on the active rosters of major league clubs (excluding time on the disabled list or any time after rosters are expanded on September 1) in their previous seasons.

Below is the summary, sorted by year from 1998 through 2018. Explanations and comments below the table. The tables below were built off THIS REPORT from Baseball-reference.com . If you are able to open in a separate tab suggest toggling back and forth.

So the first thing you may notice is that in the early days of the franchise there were very few innings being thrown by rookies. This is because it was a veteran ball club, by both necessity and design. They did not have their first amateur draft and minor league season until 1996, and by 1998-99 very few prospects were ready to reach the majors.

While the average IP per year by rookies in franchise history is 267, from 2001 onwards that average is 295.

The other thing you will notice is that I color coded IP and WAR column, and also highligted the 2003 season. 2003, also known as the year of the Babybacks, saw a whopping 609 innings taken by rookies, and they were good too, posting 11 WAR.

Brandon Webb was the headliner , posting over 180 IP and 6.2 WAR. I’m still not over Webby losing the ROY to Dontrelle Willis (3.9 WAR). The only other rookie pitcher to top 6 WAR in a season since 1986 is Jose Fernandez, in 2013. It wasn’t just Webb performing for that year’s team. Oscar Villareal, Jose Valverde, and Stephen Randolph all provided significant relief innings and value.

The next two best rookie performances after Webby were put up by Daniel Hudson in 2010 (3.8 WAR in just 80 IP) and Wade Miley, 2012, (3.1 WAR in 195 IP, 3rd in ROY). Special Mention for Micah Owings, 2007, who’s 1.6 WAR is in top 10, but also added 1.3 WAR as a batter, for 2.9 total.

Perhaps most importantly however, you will notice that quite often a lot of innings going to rookies means that the team is likely to not have a winning record. This makes sense, as it’s often due to injuries that rookies are called up. Or, if a team is losing and sells at the deadline, they call up a lot of rookies to see what they have for the future. Sometimes it works out, like 2003, but most often, there is a pretty strong correlation between rookie innings pitched and sub .500 records. In 6 of the 9 seasons with the highest IP totals by rookies, the team had a sub .500 record. You can see that by this view of the same table with season WL records added in. Sorted this time by IP.

Finally, here is one more breakdown. By General Manager.

I don’t start Joe Jr’s average until 2001, figuring the first few years with so few IP due to being new franchise would skew things. That said, the success with rookies in his tenure was almost all 2003.

The tenure averages for Josh Byrnes & Kevin Towers, are also pretty similar to Joe Jr.s.

The Tony LaRussa, Dave Stewart era produced the highest average IP and WAR by rookies, which may seem counterintuitive to some. And since Mike Hazen has taken over, the team has hardly relied on rookies at all. (Mostly because the system didn’t have many good pitchers to call up.). That could change quite a bit in 2019. They are already off to a good start with Kelly, Dunplantier and Lopez. If I were going to place a bet, I’d guess that at least 300 innings go to Rookies in 2019, and that number could easily pass 400 depending on health or trade deadline decisions.