Delmon Young and David DeJesus will be joining the Rays, Young on a minor league deal, and DeJesus either for cash considerations or for a PTBNL. That means it's time to figure out where each of them fit into the Rays lineup.
When evaluating a player's lineup impact, it's not good enough to look at overall career numbers, overall projections, or career platoon split numbers. The better way is to regress the player's platoon split and then distribute it around a projection. The idea behind regression is that we know something about David DeJesus's because he's had a long career accumulating a track record, but we also know something about him because he's a left handed hitter, and left handed hitters as a group tend to operate a certain way. The trick is in weighting the two appropriately.
The following tables are from a regression tool, made by myself and Jason Hanselman of Dock of the Rays, that implements an idea on platoon split regression put forth in The Book, but with updated regression formulas from Bojan Koprivica, and ZiPS rest of season projections. Statistics are both from FanGraphs and from Baseball Reference. Any mathematical errors are purely mine. Here's how the Rays players should be expected to perform going forward.
Potential Rays players vs. LHP:
|Player||Proj. wOBA||Career wOBA vs. LHP||Proj. wOBA vs. LHP|
Right off the bat, it's clear how Delmon Young can help the Rays. I think that his ZiPS projection is a bit rosy for a player just signed to minor league deal, but unless he's completely lost all of his ability, he'll be a huge upgrade over Matt Joyce or Luke Scott in the DH spot. With a lefty on the mound, David DeJesus should come off the bench (note that even against a lefty, DeJesus is a significant upgrade over Jason Bourgeois and Sam Fuld offensively, and shouldn't be much of a step back defensively).
Potential Rays players vs. RHP:
|Player||Proj. wOBA||Career wOBA vs. RHP||Proj. wOBA vs. RHP|
And now we get to see DeJesus's value. Facing a righty (the long side of the platoon), he projects to be the Rays' fourth best bat. Couple that with well above average defense in left field, and you have something special. Of course, assuming that Desmond Jennings and Wil Myers are healthy, they'll play. That means that DeJesus should take over left field. DeJesus in the outfield and Matt Joyce at DH is an upgrade, both offensively and defensively, on Matt Joyce in the outfield and Luke Scott at DH.
Of course, Scott is a perfectly fine DH himself when he's healthy, but at the moment he isn't. When he comes back, he may find himself as just another overqualified bench bat on an extremely deep Rays bench.