Is it time for the St. Louis Cardinals to "platoon" Jon Jay and Peter Bourjos?

Twenty-eight games into the 2015 season, the St. Louis Cardinals have an MLB-leading 21-7 record, a top-ten offense by wRC+, and a top-five pitching staff by FIP. Further, their defense (with the addition of Jason Heyward, the best defensive right fielder in baseball) projects to be even better than it was last year, and based on our editorial page, it appears Nick Lampe will have more to say about the defense tomorrow morning. While seven of the eight positions are basically set with a clear primary option, this does not appear to be the case in center field as Mike Matheny has two viable options in left-handed hitting Jon Jay and right-handed hitting Peter Bourjos. First, let's see how each of them has done one month into the season (sample size considerations):

2015 statistics

At the beginning of the season, when Randal Grichuk was healthy and readily available on the 25-man roster, it appeared Matheny was using Bourjos as the team's fifth outfielder, with his role reserved for late-inning defensive substitutions and pinch-running. After all, the Cardinals signed Jay to a two-year contract over the offseason and proclaimed on numerous occasions that he was going to be the everyday center fielder. Well, Jay's slow start at the plate, combined with Bourjos's hot start and Grichuk's back injury, has many thinking that Bourjos should start getting more playing time, with a center field "platoon" being the likely starting point.

First, via Baseball-Reference:

"A platoon is when two players share a position. The most common platoon uses a left-handed batter against right-handed pitching and a right-handed batter against left-handed pitching. Other kinds of platoons, like a good fielder/weak hitter and a weak fielder/good hitter are possible, but it's safe to assume a left/right platoon unless otherwise specified."

The Cardinals' center field situation would call for more of a hybrid "platoon" than the standard definition provided by Baseball-Reference. Keeping in mind early 2015 performance as well as career statistics, it would probably be best to start with a roughly 50:50 split of center field starts. To put it simply, this cannot be achieved by deploying a "Bourjos bats against lefties/Jay bats against righties" technique. There aren't enough left-handed starting pitchers to allow for the generic "LHB vs. RHP/RHB vs. LHP" platoon. In fact, there are only four left-handed starting pitchers in the National League Central—Travis Wood, Jon Lester, Francisco Liriano, and Jeff Locke—and only one of them (Liriano) is notably tough on left-handed batters.

Because of this, Matheny will have to look beyond pitcher handedness when deciding how to divide up playing time between the two. To be honest, three other components would likely lead to a better overall utilization of each player's assets, especially considering neither Jay nor Bourjos have a substantial platoon split at the plate.

Batted ball profiles (career) of the starting rotation

I bring pitchers' batted ball profiles up because while advanced metrics seem to love Jay's outfield defense so far this season, the sample is not big enough to be taken too seriously, as a few terrific plays (which he has indeed made, in Washington and Cincinnati) and good positioning (with the help of Chris Maloney) are probably artificially inflating his true value. On the other hand, Bourjos has proven to be an elite defensive center fielder, one of the very best in baseball, which makes it understandable to start him in games with a fly ball pitcher on the mound.

As you can see from the chart above, despite an uptick in home runs thus far in 2015, Martinez (with his power sinker and devastating changeup) is primarily a ground ball pitcher, so it would be perfectly reasonable to start Jay in El Gallo starts. Given Wacha's decreased strikeout rate and increased ground ball rate so far in 2015, Jay could probably start Wacha games as well. Now, when you look at Lynn and Lackey, with career fly ball rates of 34.3% and 35.5%, respectively, Bourjos should be paired with these starters, especially if you trust that the pitcher plays at least a partial role in the batted ball location (regarding pull %, center %, and oppo %).

Opposing catchers' caught-stealing percentages (career)

(Seven are NLC catchers and three are catchers the Cardinals will face in May)

As spokanecardsfan78 brought up in yesterday's game recap, another component Matheny could take into account is the opposing team's battery, on a game-by-game basis, when deciding who to start in center. Should there be a catcher who is particularly poor at throwing out base-stealers (such as Cervelli), it makes sense to start Bourjos, the fastest runner on the team. If a catcher effectively shuts down the running game (i.e. Sal Perez), it may be wise to start Jay. Or, Matheny could have a near perfect storm with a guy like Lester—a left-handed pitcher without the ability of holding down runners—and have zero valid reasons to avoid starting Bourjos.

Obviously, this is a much more complicated issue than just career CS% by opposing catchers, but I am confident the coaching staff of the Cardinals has scouting reports on which batteries are most vulnerable to stolen bases. In these instances, Matheny should start Bourjos, especially if scoring runs will come at a premium (i.e. versus another team's ace). On a completely unrelated note, looking at this chart makes me appreciate Yadier Molina even more as his career CS% is 45%, with the league-average CS% being 28% over the course of his 12 years as a major leaguer.

Strikeout rates among National League starting pitchers (since 2010)

Bourjos has a notoriously high strikeout rate in his career at 23.0%, while Jay strikes out considerably less at 15.6% of the time. Thus, starting Jay with a high strikeout pitcher on the mound makes sense. With five of these pitchers being left-handed (and also tough on left-handed batters), Bourjos is still probably the better option in some of these situations, despite his high strikeout rate.

Bottom line

At present, should there be a "platoon" in center field for the St. Louis Cardinals? In my opinion, the answer to this question is a resounding yes. Down the road, as performance samples grow for both players, one may begin to stand out and subsequently deserve more than just a 50:50 split of playing time. However, being barely over one calendar month into the 2015 season, we are not there yet, and we cannot simply replace past performance with what we have seen from each player in 28 games. Thus, I have provided three possible components for Matheny to consider (beyond LHB vs. RHP, RHB vs. LHP) when deciding who to start in center field. As I wrote last August, Matheny did pretty well managing center field in 2014. Here's to him managing the position even better in 2015.

As always, credit to Fangraphs and Baseball-Reference for statistics used in this post.