Platooning Justin Ruggiano

Yesterday, the Mariners addressed their outfield deficiency by acquiring Justin Ruggiano from the Chicago Cubs. As Scott pointed out in his overview, he's a low-cost outfielder who fills a need, balances the lineup, and could be used as one half of a right field platoon. He also leaves room for the Mariners to be flexible if needed. He's probably not going to play every day but he could split time in both right field and left field.

It's this very situation I want to examine in a little more depth today. What would platooning Justin Ruggiano look like, statistically, for the Mariners?

It would be easy to point to his career wRC+ of 128 against lefties and call it good but we know better than to take a simple split at face value. Ruggiano won't only ever face lefties so we have to adjust for his expected playing time against righties and lefties. We also have to consider the sample size for the split we're using as well as the offensive output of his platoon partner. It gets pretty complicated pretty quick.

Thanks to the research done by Matt Klaassen and Tom Tango we can pretty easily estimate a hitter's platoon skill. Logan has done this before when the Mariners signed John Buck last year so I won't rehash the gritty details. The short of it is: to determine the projected platoon split for any given player, we must regress towards the mean to estimate based on their observed performance. Once we've established an estimated platoon split for all the parties involved, we must adjust each player's performance based on the estimated percentage of plate appearances against both left- and right-handed pitchers.

I'll be using wOBA for the initial calculations and then I'll convert to wRC+ afterwards.

Editors note: the calculations below  for left-handed batters have been updated to account for a regression error.

Let's start with Justin Ruggiano, the right-handed portion of any platoon the Mariners might run out in right or left field. Ruggiano has a career .329 wOBA; his wOBA jumps up to .360 in 443 plate appearances against lefties and drops to .312 in 806 PA against righties for a difference of 14.6%. Using the method laid out in the articles above, we come to a regressed platoon skill of 7.5% -- ((.146*443)+(.0611*2200)/(443+2200)). Using his Steamer projected wOBA, I "centered" his regressed platoon skill based on the percentage of plate appearances Ruggiano has had against lefties (35%). This gives us an estimated platoon wOBA of .326 vs. LHP and .303 vs. RHP. Those two marks translate to a wRC+ of 113 and 96, respectively.

Okay, what about Ruggiano's platoon partners? As the roster stands, the most likely platoon partner would be Brad Miller. Here are the relevant inputs:

Plugging these in gives us an estimated regressed platoon wOBA of .334 vs. RHP and .302 vs. LHP. Translated to wRC+, that's 118 and 96, respectively. To combine the platoon skill of Ruggiano and Miller, I used a simple weighted average based on the percentage of plate appearances against each type of pitcher. This gives us a combined estimated wRC+ of 106 for a Brad Miller/Justin Ruggiano platoon in right field.

What about a situation where Ruggiano splits time with Dustin Ackley? Here are Ackley's relevant inputs:

Plugging these in gives us an estimated regressed platoon wOBA of .329 vs. RHP and .304 vs. LHP; a wRC+ of 115 and 97, respectively. The combined estimated wRC+ for a Dustin Ackley/Justin Ruggiano platoon would be 105.

So our internal options make for decent platoon partners for Ruggiano, both of them combining for a wRC+ that's just a bit above average. What about some of the external options that have been mentioned recently, Seth Smith or Nori Aoki?

Here are Smith's relevant inputs:

Wow, there's a massive 25% gap in Seth Smith's observed split. This gives us an estimated regressed platoon wOBA of .367 vs. RHP and .321 vs. LHP; a wRC+ of 141 and 109, respectively. Combined with Ruggiano, that's a 117 wRC+, a very good mark.

Here are Aoki's relevant inputs:

Remember, Nori Aoki has run a reverse split over his career. When we plug these inputs into our regression calculator, his platoon wOBA comes out to .327 vs. RHP and .316 vs. LHP. By regressing towards the league average (a 8.6% difference for left-handed batters), Aoki is estimated to reverse his reverse split. This is just a rough estimate and a baseline with which we're trying to get a glimpse of a potential future. Platooned with Ruggiano, Aoki combines for a wRC+ of 106.

Each of the options I listed above calculates to be above average options for the Mariners. Here's a table of the results with a cherry-picked addition:

None of the options I went through can beat the production of Justin Upton though Seth Smith and Justin Ruggiano could come close. We shouldn't be discouraged that these options fall short of Upton however. Any of the options I listed would be vastly cheaper than Upton and could potentially provide more flexibility for the Mariners. And the two internal options still leave room for another acquisition if the Mariners find one to their liking. Seth Smith looks more and more like a prudent acquisition if the Padres are willing to part with him. Now that they've acquired their eighth outfielder (including Matt Kemp and Wil Myers), they have parts to spare.

The Mariners are almost there. They could field a competitive team if the season started tomorrow and have the flexibility to add another piece if they wanted. It's amazing how one little move can have massive ramifications but that's what happened when the Mariners acquired Justin Ruggiano. Let's see if Jack Z has one more piece of the puzzle up his sleeve.