So I started today looking at the third base, center field, and right field platoons for the Kansas City Royals and I how I think they could maximize the potential for those hitters in the lineup throughout the season. I did that partly in preparation to take a look at the St. Louis Cardinals and possible platoons there.
The Cardinals, quite frankly, can not know with certainty how Kolten Wong will hit at second base. They can hope that he'll hit like he did in the minors. Speaking of which, in the minors, Wong faced 72% RHP (as a lefty hitter) and hit .309/.378/.463/.841 against those RH pitchers. Against lefties (28% of the time) he hit .285/.337/.408/.745. That's not a small platoon split, but it is about normal for a player to be a bit worse against the same-handed pitcher, as Wong has been at those levels. Overall in the minors, he hit .302/.366/.447/.813.
My projections for the 2014 version of Kolten Wong is .265/.324/.389/.713 at the major league level. You can see that this is much worse than his career numbers in the minors, as it should be. I have him 37 points worse hitting, 42 points worse getting on base, and 58 points worse slugging. If I take those amounts off of his hitting against both left-handers and right-handers, here how the projected splits would look in the majors for next year:
Overall - .265/.324/.389/.713
v. RHP - .272/.336/.405/.741
v. LHP - .248/.295/.350/.645
On the other side of the platoon at second base would be right-handed hitting veteran Mark Ellis. He has a lot of career data at the major league level to go on, so we'll use that data.
Overall - .270/.323/.351/.674
v. RHP - .265/.319/.325/.644
v. LHP - .282/.331/.412/.743
As you can see, Mark Ellis is much better against left-handed pitching than he is against right-handed pitching, and much better than Wong against the same. Much the same meanwhile, Wong is likely to be better against RHP.
Like I did with the Royals, I'll assume that the second base (and center field later) platoon(s) will have 700 PA split between the two hitters. I will also assume that the Cardinals will see about 70% right-handed pitchers this year and about 30% left-handed pitchers this year. One last assumption is that a strict platoon where the left-handed hitter faces 100% RHP and vice versa is not possible. I'll assume a very well played platoon by the manager as 80% against opposite-handed pitching and 20% against same-handed pitching.
If Ellis and Wong were just thrown out there for 490 PAs given to Wong and 210 PAs given to Ellis, they would be projected to hit a combined .267/.324/.378/.701. However, if platooned very well by Mike Matheny, they would project to hit a combined .271/.328/.394/.722. There does not seem to be much of a difference at first glance, but the slugging added - partially aided by a slight bump in batting average - is the difference between being a Jose Altuve type hitter slapping the ball around and a Kelly Johnson type with more walks.
Overall - .293/.356/.400/.756
v. RHP - .300/.360/.417/.777
v. LHP - .269/.343/.346/.689
Overall - .251/.306/.398/.704
v. RHP - .249/.309/.394/.703
v. LHP - .256/.301/.405/.706
They have both actually hit around the same against lefties and righties, except Jay's power numbers against left-handed pitching have been lacking. Bourjos has actually been slightly better at average and power against lefties and walking against righties.
A straight platoon of the two would be the least good option. If you just gave Jon Jay 50% of the PA and gave Bourjos 50% of the PA without looking at handedness, the two would be projected to combine for a .272/.331/.399/.730 line.
If you were to give Jon Jay 70% of the plate appearances due to ~70% of pitchers being RH - but NOT aligning Jay to the righties and Bourjos to the lefties as much as possible, just randomly playing them those percentages, the line for the two combined would sit at .280/.341/.399/.740. There would be no difference slugging, but the ISO would go down and the OBP would go up along with the OPS. This is a better line, but not as well as it could be.
If you were to give Jay around 75% of the PA against righties (370 out of 490) and Bourjos around 85% of the PA against lefties (180 out of 210), you'd end up getting Jay 350 PA and Bourjos 350 PA. Using that platoon split, their line would be .279/.335/.407/.742. This is likely the best of the bunch with a .742 OPS, a slight boost in power, and getting Bourjos at least 300 PA, especially with his great speed and defense.
Compare the three yourself to see:
.272/.331/.399/.730 (50-50 split with no regard to handedness)
.280/.341/.399/.740 (Jay 70%, Bourjos 30%)
.279/.335/.407/.742 (Jay 400 PA, Bourjos 300 PA, platooned well.)
Then again, before last year's wrist injury, Bourjos was hitting .333/.392/.457/.849 over nearly 150 PA! If he hits anything close to that, then go ahead and just play Jay 10% of the time against lefties and enough against righties to keep him sharp off of the bench and get Bourjos 550+ PA!
Then again, after last season's slump to start the year, Jay was hitting .322/.391/.424/.815 over his last 270 PA last year. If he hits anything close to that, then go ahead and play him 550+ PA and give Bourjos the defensive specialist role and start him against lefties.