The Arizona Diamondbacks and the need for pitching depth

On Opening Day 2017, the Diamondbacks’ rotation was Zack Greinke, Patrick Corbin, Taijuan Walker, Robbie Ray and Shelby Miller. They combined for a decent 124 starts between them - all except Miller made at at least 28. But this still left 38 starts which needed to be covered by Arizona’s pitching depth, in various forms. These were covered by five other starting pitchers. Most of them came in the shape of Zack Godley (25), but we also saw Randall Delgado (5), Anthony Banda (4), Braden Shipley (3) and T.J. McFarland (1). While the combined record of these five wasn’t that good, at 9-15, their ERA (again, mostly thanks to Godley) was 4.19. That’s great, considering the average NL starter had a 4.44 ERA.

Fast forward a year. More than three-quarters of those replacement starts will no longer be available in 2018. Godley will be in the rotation, replacing the Tommy John’d Shelby Miller, and Banda is now a member of the Rays. The odds are, the team will probably need a comparable number of stand-in games this year, because it’s highly unlikely you can get through a season using just five starters. In Arizona history, the actual number used has fluctuated between six (in 1999) and twelve (in 2015). I thought it might be worth digging a little further into the past seasons, to give us an idea of how many starts we will need to cover with pitchers not in the Opening Day rotation, and when that might start.

The chart below shows, for each year in franchise history, the first five pitchers to start games for the D-backs. They are listed in chronological order, without regard for skill. The last three columns are the game number (from #6-162, obviously) where a sixth starter was first required, who that was, and the total number of starts made by #1-5. I have adjusted this for cases where the obvious Opening Day starter was injured - otherwise, they would be seen as a replacement, not the player in the Opening Day rotation. For example, as we’ll see, Enrique Gonzalez was the actual fifth starter used in 2008; the sixth was Randy Johnson. I’ve flipped those for common sense reasons!

Looking at the above, the number of starts from the effective Opening Day rotation ranged between 86 and 145, with an average figure of 118. In other words, in a typical season, the D-backs have had to find 44 starts from pitchers outside of the front-line five - basically, close to needing another starter and a half. And it usually hasn’t taken long, typically 30 games, for that need to arise. Sometimes, the rotation hasn’t even made it through spring training. In 2008, the Big Unit was the early #1 starter for the Tucson Sidewinders, as he rehabbed from back surgery, hence the early need for Gonzalez. The following year, of course, saw Brandon Webb’s major-league career end on Opening Day.

So it’s important to realize, even if our expected rotation perform as they did last year, that would not be enough to repeat last year’s pitching success. Because either they’ll have to make more starts, or the depth behind them will also have to be as good as it was in 2017 - and that’s better than the NL average starter, remember. It’s going to be a tough act to follow, for Matt Koch, Braden Shipley, Albert Suarez or whoever it ends up being in the sixth rotation spot and on down. I’ll take a look at the specific candidates in a bit more depth, as a future article.