How Much Does Reno Inflate Hitters Numbers?

Something Diamondbacks' fans have become used to over the past few years, are the extraordinary stats put up by hitters at our Triple-A affiliate, who moved to Reno from Tucson before the 2009. Every year, it seems we hear reports of players, whether unsung prospects of career journeymen hitting near .400 and knocking the ball out of the park with Ruthian authority. And, almost as inevitably, when these players get called up the big-league club, they fail to deliver anything like their Reno lines.

The poster-child for this is probably Brandon Allen, who had a .966 OPS, including 43 homers. over 846 PAs with Reno. But he failed to get anywhere near that above AAA: he only hit .213 for the D-backs, was subsequently dealt to Oakland, failed to stick there, and is was recently put on waivers by the Rays organization, who picked him up after he was previously put on waivers by the A's. So how much should we discount Reno numbers?

There are two main reasons for the drop-off between the offensive stats with our Triple-A affiliate, and the majors. One isn't unique at all: you face significantly better pitchers here than in the minors. But the other is particular to the location. Reno remains very hitter-friendly, though inflates home-runs less than you'd expect, because it's very capacious - the park is a monstrous 424 feet to the fence in right-center, and has a "mini Green Monster" in left-field, to help compensate for the altitude. At 4,600 feet, it's far higher than any ballpark in the majors except for Coors Field, more than four times the distance above sea-level of Chase. And there's no humidor in Reno.

This affects both hitters and pitchers. Barry Enright had a 5.21 ERA in 2011 with Reno, the best on the team of any pitcher with 60+ innings. It was also higher than his 4.87 major-league career number, despite the lower quality of hitters. He talked about this after the season: "This biggest challenge pitching in a high altitude ballpark like Reno is not changing who you are. Going through a year in Reno with the pitching difficulties is just as much a mental challenge as it is physical... People don’t realize the challenge it is until they go through it themselves, but like I’ve always told people if you can pitch in Reno and have success you can pitch and have success in the big leagues."

For now, however, let's stick to offense. To measure the effect this has on those numbers, we looked at everyone who had more than 50 PAs for both Reno and the Diamondbacks during the same season (to help reduce the effect of aging or other longer-term changes in performance), since the Aces became our affiliate in 2009. This included both prospects who were called up to the big-league club, and major-leaguers who spent significant time in Reno, on rehab or other assignment. The chart below shows their numbers in both environments. [A full breakdown, including the raw numbers for the players, is available in this spreadsheet]

Of course, it does vary. greatly from person to person: Chris Young, John Hester and Sean Burroughs all had a Reno OPS more than 400 points better. Rusty Ryal in 2009 actually bucked the trend, with a better OPS in the majors that year - though that was likely a statistical fluke, resulting from the small sample size of 68 MLB plate appearances. If we look at his overall major-league OPS of .721, that comes in well below the .859 career Reno figure. .

But if we take the overall difference across all qualifying hitters, these numbers result from a total of 6,196 PAs, almost four thousand with Reno and the balance in the majors, so we are talking about a fairly significant amount of data. To sum up the results there in round numbers, they suggest that moving from Reno to the major-league will knock about 80 points off your batting average, 100 from your OBP and deduct 140 points off your SLG, for a total loss of 240 points from the expected OPS.

If we apply the suggested correction to someone like Allen, this is what we get:
Reno line: .281/.415/.551 = .966 OPS
Projected D-backs line: .201/.315/411 = .726 OPS
That turns out to give a surprisingly accurate prediction of his big-league numbers with the team.
Actual D-backs line: .213 /.325/.404 = .729 OPS

Only one player in 2012 has reached the necessary 50 PA cutoff in both locations, A.J. Pollock. I didn't include him in the overall chart, but what does the system have to say about his expected performance?
Reno line: .352/.396/.440 = .836 OPS
Projected D-backs line: .272/.296/.300 = .596 OPS
Actual D-backs line: .245/.288/.340 = .628 OPS
Again, not too far off the mark.

Foe players who do have major-league experience, I would probably still lean towards using those numbers in preference to adjusting the Reno stats. For instance, I would be inclined to wager that Josh Bell will hit closer to his previous MLB line of .202/.223/.265 than his Reno-adjusted one of .301/.329/.479. But with players where you don't have the major-league stats, it might be useful. For instance, Ryan Wheeler's .345/.386/.552 AAA line looks pretty decent; but when you adjust it, you get a projection of .265/.286/.412, a .698 OPS that is less appealing [though really, it's still better than the .670 produced by our third-basemen at the time of writing]

Let's take a look, to see if we can find out what parts of a hitter's stats show the changes that take place. The table below breaks down the plate appearances from the qualifying hitters above, by result:

This does support the idea mentioned above, that the capacious dimensions of Reno's park help make it a triples-happy field, with almost two and a half times the frequency of three-baggers at Triple-A that we see in the big leagues. Home-runs are about 40% more common, singles and walks increase by a third. Doubles don't decrease that much in the majors, and strikeouts, despite the better quality pitchers faced there, are hardly changed at all. which is somewhat of a surprise.

Finally, is there anyone in Reno who could help Arizona right now? The current Diamondbacks major-league OPS is .742, so if we add the Reno adjustment to that, we'd be looking at a .982 OPS there - obviously, the exact break-even point depends on position, etc. but this is good enough for a rough line. There are currently two regulars in Triple-A above that, and a third less than a handful of points below it. Here's the stats thus far for all three

Ruiz has major-league experience, with a career line in 238 PAs of .272/.332/.488, and .820 OPS, so might have value. However, 1B has been fine for the D-backs, with Lyle Overbay and Paul Goldschmidt both producing more than acceptably this year. Elmore has flown under the radar [or had, until Nick Piecoro wrote about him on Saturday, Reno's Brett Butler calling him "the best two-hole hitter I’ve ever had"], but has almost no power - just one home-run - though you can't complain about a K:BB ratio of 24:38. That kind of contact and plate discipline are adored by Towers and Gibson. However, Aaron Hill's .768 OPS is, again, not an area where I'm feeling much concern.

Obviously, the D-backs outfield is crowded enough, and has no room for Eaton at this point. The key words being "at this point". His presence, along with A.J. Pollock, and projected production does seem to give the team depth there which would allow them to deal one of the current members (say, for a young short-stop to replace Drew) without too much impact. As shoe noted a while back, that good OBP and Eaton's wheels - he has been successful in 18 of 20 stolen-base attempts this year - would seem to make Eaton a genuine lead-off hitter, something we haven't had for a very long time, if ever. We'll see what happens the rest of the year.

[All stats in this piece are through Friday night]