Last week, Ben discussed the workload of Yadier Molina and his status as one of the most-used catchers in all of baseball. Molina's defense is clearly valuable to St. Louis, and St. Louis owes much of its success to his abilities behind the plate. In the last three seasons he has taken his hitting new heights, turning himself into an MVP candidate. Catching every day takes a toll on all players, and Molina is no different. Catching on multiple days without rest decreases his performance at the plate.
From 2011-2013, Molina has been excellent on offense, posting a .313/.361/.481 slash line good for a .364 wOBA. His 133 wRC+ is second only to Buster Posey among full-time catchers and 28th out of the 226 qualified hitters over that period. Because of his status as an elite defender as well as a very good hitter, lip service is paid to keeping him fresh throughout the season. Molina's second half numbers certainly do not support a drop in play over the course of the season as he has put up wRC+ of 152, 146, and 112 over the last three seasons. However second half numbers alone do not tell the full story when it comes to fatigue.
Playing day after day without rest could take a greater toll on a catcher in individual games as opposed to general wearing down throughout the course of the season. To test out Molina's resilience, determining Molina's offensive numbers depending on how many games he has played in a row could shed some light on potential fatigue for Molina. Because Molina's offensive numbers have only been consistently solid from 2011 forward, I used those three seasons to see if there is a difference depending on days played in a row. If Molina did not play catcher and have at least two plate appearances, I considered that a day off.
Keeping in mind that offensive statistics stabilize with different plate appearance levels (910 AB for BA, 460 PA for OBP, 320 AB for SLG, and 160 AB for ISO), here are the statistics for Molina depending on days at catcher in a row.
Molina holds his batting average and on-base percentage fairly static across the categories, but his slugging and isolated slugging plummet when he plays at least five days in a row. In graph form (plate appearances in parentheses):
The differences seem more stark in graph form. While there is really nothing the Cardinals can do about the drop in power playing two days in a row, the Cardinals can do a lot better about preventing Molina from playing catcher five straight days. Molina has actually been worse during the past two years, posting decent numbers with less rest in 2011.
It is too early to know if the drops in on-base percentage and batting average are evidence of Molina's tiring, but the drop in power is still convincing enough to consider getting Molina an occasional day off during a long run of games. In practice, ensuring Molina does not work five days in a row takes some planning. The Cardinals have twelve sequences of at least five games in five days during 2014 uninterrupted by an off day or a series where the designated hitter is used. Five of those sequences are of at least thirteen games. By timing Molina's days off strategically, Matheny could give Molina twenty games off behind the plate and only have him catch on a fifth consecutive game three times. Of those twenty games, twelve would occur on either a day game after a night game or a night game prior to a day game.
Molina's importance behind the plate and influence on the pitching staff cannot be discounted. As Molina has generally kept up his average and on-base percentage, his eye and reaction times are not likely in doubt meaning his defensive value is likely close to when he is fresh. Getting behind the plate many days in a row saps Molina of his power, which has been a big driver in his increase in performance over the past three seasons. While Mike Matheny may prefer to go day by day and see how Molina feels on any given day, planning ahead and ensuring that Molina's days off are a little more well-timed could increase his effectiveness at bat in 2014.