The Curious Case of Pedro Alvarez and his Diurnal Explosion

(Gene J. Puskar / AP)        

By Stevo-sama | @yoshiki89

There has been some discussion, most recently following the Pittsburgh Pirates’ dramatic 19-inning win over the St. Louis Cardinals, surrounding Pirates infielder Pedro Alvarez and his peculiar AVG/OBP/SLG day/night splits this season.

In 582 AB during the 2010 and 2011 seasons, Alvarez was batting .241/.313/.354 (158 AB) in day games and .226/.301/.406 (424 AB) in night games, a percentage difference of 5.8% in OPS. However, in 2012 so far Alvarez’ day/night splits are profoundly shocking. In 125 AB, Alvarez is batting .312/.385/.752 in day games and 255 AB, .196/.280/.322 in night games. His most notable conventional offensive metric is his HR rate in those ABs; he’s hit 16 HR in 125 AB (12.8%) during the day, 7 HR in 255 AB (2.7%) at night.

There have been other notable day/night splits poster children in recent seasons. Justin Morneau’s 2011 splits found him struggling considerably during night games after several fairly consistent seasons (Day: 100 AB, .320/.361/.490; Night: 164 AB, .171/.239/.238). Morneau’s troubles may or may not have begun after his mid-2010 concussion (he finished the season with a 1.13% difference in OPS between day and night), but there’s enough doubt around his lingering symptoms starting in 2011 to perhaps explain the drastic change during that season. What isn’t easily explained is why, in 2012, Morneau is experiencing a swing in the opposite direction, .682 OPS in 129 Day AB versus .870 OPS in 256 Night AB.

Luke Hochevar is another infamous seasonally inconsistent day/night performer. In 2008, Hochevar was 0-3 8.27 ERA in 4 starts during the day and 6-9 4.98 ERA in 18 starts during the night. His splits normalized from 2009-2011 (a 1.5% difference in ERA for those 3 seasons), but he returned to his favoritism of baseball under the lights this season, 1-5 8.27 ERA in 8 starts during the day and 6-6 3.82 ERA in 17 starts at night.

What can be made of day/night splits? In this spring 2010 Baseball Prospectus article, Russell Carleton reiterates what is really known and understood about drawing relevant conclusions from stats found in day/night splits…those stats always end up in the general duty bucket of “small sample size.” Carleton asserts that even with split-half reliability correlation, traditional triple-slash stats are simply not reliable enough to provide a specific foundation for predictive analysis. In his own words, “the practice of using split statistics is taking a stat that is already a little unreliable and cutting its underlying sample size in half…which makes it an even more unreliable measurement.”

It’s true that Alvarez’ whopping 61.5% difference in 2012 day/night OPS is significantly higher than Carleton’s examples from two years ago, but the question remains: which of Alvarez’ triple-slash day/night splits are more predictive and less small sample size? With the difference in nearly 70% of AB between day and night, the assumption can be made that his daytime production has a greater likelihood of panning out to be closer to his less-phenomenal nighttime production, over time and with a larger sample size to analyze.

That being said, with his current daytime ballistic OPS, is it fair to assume that as Pedro Alvarez goes at night, so do the Pirates? And will this hold up for the Pirates throughout what’s left of the 2012 season?

As of August 21, the Pirates are 27-15 in day games and 40-40 in night games. The team isn’t either winning more games or losing fewer games during the day, depending on how you look at it. Are they reaping any benefits from Alvarez’ diurnal emissions as far as scoring runs concerned? During day games, the Pirates are scoring 4.5 runs per game, as opposed to 3.9 runs per game during night games. It would seem that when Alvarez is contributing to the offense, the Pirates are doing better.

The most notable metric to consider is his aforementioned HR rate. If you can expect Alvarez to present a tater while at the plate in just over one of every 10 at-bats, this is a formidable factor in scoring runs that will ultimately lead to winning games…and winning is ultimately the only parameter that matters. However, the Pirates are playing almost twice as many night games as day games, so this too can be considered a flawed analysis due to small sample size.

As we prepare to enter the home stretch of the season and the Pirates can legitimately claim they are making a run for the playoffs (even if only as a Wild Card contender), it’s certain that they (particularly Pedro Alvarez) may have less of a chance in success during postseason play – games that are always played at night, if these splits maintain their shape. However, there is hope! If the postseason were to start today and the Pirates were to secure that Wild Card spot, they would face the Nationals in the first round. The Pirates are 3-2 against the Nationals in 2012 and all of those games occurred at night.

But one shouldn’t expect Alvarez to be a factor in that theoretical contest; he’s batting .063/.118/.063 against the Nationals in those 5 games.

Otherwise known as "The Baseball Enthusiast," Stevo-sama is a scorekeeping addict who scores every game he watches and/or attends, and typically posts these scoresheets on his blog with a game story of one sort or another. Stevo is a self-proclaimed proponent of the Scorekeeping Revolution, community member of the Eephus League, and proud member of the Baseball Bloggers Alliance.