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Brewers Rookie Junior Guerra’s Place in History

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The 31 year old treated fans to a once-in-a-lifetime debut season.

Los Angeles Angels of Anaheim v Milwaukee Brewers Photo by Mike McGinnis/Getty Images

Over the weekend, Milwaukee Brewers manager Craig Counsell announced that Junior Guerra was going to be shut down for the remainder of 2016 after reaching his innings limit. That closed the book on a sensational rookie campaign for the 31 year old, one that almost no one (ahem) can claim that they could have predicted. But the #2016BrewersAce didn’t have just a great season, he had a historically significant one.

Junior finished the year with 121.2 innings pitched in 20 starts after debuting against the Angels on May 3rd. His 2.81 ERA was the lowest among Brewers’ starters by over a full run-per-nine (Zach Davies, 3.92) and he was far-and-away the staff’s RA9-WAR leader at 3.9 wins above replacement (Tyler Thornburg, 2.7). Among National League rookie starting pitchers this season, Guerra sports both the best earned run average (min. 70 IP) and highest RA-9 WAR, beating out Kenta Maeda, the Dodgers’ Japanese import, in both categories (3.24, 3.6). His ERA- of 66 is also tops among NL rookie starters, ahead of Tyler Anderson of the Rockies (75) and Maeda (82). Guerra should rightfully earn some down ballot Rookie of the Year votes for the tremendous results that he churned out this year on the mound.

Beyond that, however, Guerra also turned in one of the finest campaigns in recent memory for the Milwaukee Brewers franchise. Only four times since the turn of this century has a starting pitcher for the Brewers thrown more than 100 innings while turning in an earned run average below 3.00. Those players are:

Jeff D’Amico - 2000 (2.66 ERA in 162.1 IP)
Ben Sheets - 2004 (2.70 ERA in 237.0 IP)
C.C. Sabathia - 2008 (1.65 ERA in 130.2 IP)
Junior Guerra - 2016 (2.81 ERA in 121.2 IP)

Dating back to the start of the Divisional Era and creation of the expansion Seattle Pilots and eventual Brewers in 1969, 37 players in the organization’s history have thrown at least 70 innings as a starter during their rookie campaign. Of those, only Cal Eldred can boast a better rookie season ERA than Junior Guerra this year, thanks to his magnificent 1.79 mark across 100.1 frames during his rookie campaign of 1992. Guerra’s RA-9 WAR ranks third all-time among Brewers’ rookie starters, behind only Eldred’s 4.5 in 1992 and the inaugural season of Bill Parsons’ short-lived career, when he notched a 4.0 tally in 1971. Guerra’s 66 ERA- stands as the seventh-lowest single season mark in club history among starters with 70 innings pitched and the second-lowest mark by a rookie.

Guerra’s advanced age also brings another unique historical context to his first season in Milwaukee’s starting rotation. Since the beginning of the Divisional Era, only 44 hurlers have worked their rookie campaigns at age 31 and thrown a minimum of 10.0 innings, so we’re already looking at an exclusive club. Breaking it down further, here is the list of 31 year old arms who have thrown more than 100.0 innings in during their rookie season:

Hisashi Iwakuma - 2012 (125.1 IP)
Junior Guerra - 2016 (121.2 IP)

And the list of 31 year old rookies to make at least 20 starts:

Junior Guerra - 2016

Among the above stated group of 31 year old rookies with 10.0 innings, Guerra was by far the most valuable, besting runner-up Brendan Donnelly’s 2003 campaign out of the Angels bullpen (3.5 RA-9 WAR) by nearly half a win.

Junior Guerra treated fans of our local nine to a truly once-in-a-lifetime season this year while firmly staking his claim to a spot atop the Brewers’ starting rotation for next season. Guerra’s singular debut has already placed him in the annals of franchise and league history, and with five years of club control remaining Junior’s surprising ascension could help spur a quick return to competitive baseball here in Milwaukee.

Statistics courtesy of Fangraphs