Matt Holliday's power is on the rise

Matt Holliday came into 2014 with incredible career numbers. His career slash line coming into this season was .313/.387/.536 with a wRC+ of 139. Since coming over the Cardinals he has maintained the numbers he had when Coors Field was his home park with a .305/.389/.515 slash line with a wRC+ of 145. As offense has declined throughout baseball, Holliday's numbers have actually gone up relative to the league. For the first few months of 2014, the 34-year old looked to be on the decline, but Holliday has come on recently, providing hope for a monster second half.

The biggest sign of a decline for Holliday this season has been his drop in power. As recently as three weeks ago, Holliday's slugging percentage on the season was just .389 and his ISO (SLG-BA) was only .117, a far cry from his career .536 and .223 respectively. Due to a high on-base percentage, Holliday has remained a productive hitter all season, but had yet to unleash his signature power numbers. To provide a sense of Holliday's progression on the season, here is a graph showing Holliday's wRC+ over this season broken down into six roughly equal parts. The cumulative wRC+ as well as his career numbers are also shown.

From the 4th of July forward, Holliday has hit .295/.394/.607 with a wRC+ of 180. Getting slightly more arbitrary, in his last 13 games since July 8th, Holliday is hitting .333/.423/.733 for a wRC+ of 220. As the chart above shows, Holliday was sitting mostly solidly above average around the 110-mark before showing an uptick in the fourth and fifth sections before going crazy in July. His slugging has been in question this season. Here is the same chart as above for slugging percentage with ZiPS preseason projections included as well.

His slugging percentage stayed around league average (.390) before moving up over his last two sections. His current line of .418 is still well below his career average and his ZiPS projection of .468, but it has gone up almost 30 points in just the last few weeks. As slugging percentage can be dependent on batting average, here is a graph of his isolated slugging over the same period.

Looking at his ISO shows that his power actually returned in the 4th section (late May) of plate appearances. Because he had a very low BABIP at that time, his power was hidden in his slugging numbers during that period. His season stat line is very close to his projections from the beginning of the season for ISO. A continued surge over the rest of the season may still see his seasonal statistics fall short of his career norms, but he has a much better chance to get closer than he did one month ago.

Looking at Holliday's statistics in this manner shows two dangers in looking at small sample sizes. First, it shows how much, even over just three weeks, a seasonal line can change. This should provide caution in writing off consistent performers whose numbers look below expectations, especially when the numbers provided are still productive and helping the team like Holliday. At the end of the season, there are fewer surprises compared to looking at the numbers after a month, two months or at the All-Star break. Numbers will fluctuate throughout a season and focusing too much on one month or one half can be deceiving which brings us to the second danger in looking at statistics over small periods.

Holliday's recent numbers could be just a blip, as anything can happen over a short enough period. Certainly Holliday's numbers are encouraging, but they do not necessarily mean he will hit this way for the rest of the season. Holliday is at an age where players tend to decline, although Holliday has bucked those trends over the last several years. The main reason to be optimistic that the recent surge by Holliday will continue, but probably not quite this well, is that the numbers come closer to our expectations.

Holliday's recent uptick in numbers tends to confirm what we believe will happen and is more reliable than if Jon Jay put up the same numbers over a three week period. We would expect that Jon Jay's numbers would revert back to something more consistent with his career. When the numbers are consistent with Holliday's career it is much easier to believe that he will continue to perform. Since May 23rd in 223 plate appearances, Holliday is hitting .277/.386/.473 with an ISO of .197 and wRC+ of 145. His power is back, and it is fair to expect a really good second half from St. Louis' best hitter since Albert Pujols left for Anaheim.