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Peter O’Brien: For real?

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This year, the slugger has made a huge, late-career breakthrough. But is he here to stay?

MLB: Miami Marlins at Washington Nationals Scott Taetsch-USA TODAY Sports

For Marlins fans, this week in baseball sucks. The end of a grim, first rebuilding year has mercifully come with the Marlins set to finish just shy of 100 losses. I’m pretty sure our Slack was more excited about the Instructional League game earlier Wednesday at Marlins Park than the actual game. Rest assured, however, I know I’m going to be sad when the “WE ARE...FOX SPORTS” jingle doesn’t boom through my apartment on a daily basis anymore. It’s a lose-lose scenario for all of us.

But as I always do, I’ll remind you now: there are bright spots. One of those bright spots is the Marlins newest, handsome, large adult son, Peter O’Brien.

For the less engaged in MLB prospects, the 6’4”, 235 pound, human Robocop seemed to materialize out of thin air. In a system brimming with new toys like Monte Harrison and Isan Diaz, no one really paid attention to O’Brien at the bottom of the box.

But after about 80 games of absolutely mashing in Double-A and Triple-A, the 28-year-old was given the call-up for roster expansions. And he hasn’t stopped mashing yet. With 19 games under his belt, O’Brien has accrued an OPS of .935, a wOBA of .390, and a wRC+ of 151.

Our editor Ely heralded the arrival of O’Brien with cautious optimism earlier this year:

Now 28 years old, O’Brien is certainly not a priority. Let me make that clear. That being said, his path to The Show is more realistic than it might’ve seemed a week ago. Garrett Cooper was closing in on reclaiming the same kind of role on the Marlins before re-injuring his wrist.

Almost a month later, is that still the case? Can the former perennial Top 10 Diamondbacks prospect make enough of an impact on the Marlins brass this year to stay in the conversation? Or will the late-season breakout be too-little-too-late, forcing him to go the way of Scott Van Slyke next spring?

Peter O’Brien 2018 Stats

Team G PA 2B HR BB% K% OBP SLG OPS wOBA wRC+
Team G PA 2B HR BB% K% OBP SLG OPS wOBA wRC+
LAD AA 31 112 3 7 8.9% 39.3% .241 .390 .631 .282 69
MIA AA 43 174 4 13 16.1% 28.2% .345 .514 .859 .377 138
MIA AAA 36 135 6 10 14.8% 29.6% .385 .598 .983 .415 150
MIA 19 60 4 4 10.0% 33.3% .350 .585 .935 .390 151
Fangraphs

As we can see, O’Brien made some kind of breakthrough early on in the season. His previous struggles go much further than this April, however. O’Brien was traded for the second time in his career by the Diamondbacks after scuffling between Triple-A and the Bigs. In 2017, O’Brien scuffled in abbreviated stints with four separate teams, before settling in for the better part of the season with the Dodgers’ Double-A Tulsa Drillers. With Tulsa, O’Brien milked a .465 SLG into a .340 wOBA, despite getting on base at a clip of just .297, and striking out in nearly half of his plate appearances.

O’Brien’s woes continued with the Dodgers this year, and this time, he couldn’t rely on the long ball to bail out his poor approach. He was again plagued by poor plate discipline, an attribute that he has been saddled by since 2016.

But upon coming to the Marlins, O’Brien clearly made a serious adjustment to his approach. In as many games in Double-A Jacksonville this year, O’Brien has struck out the fewest amount of times since he was in Triple-A Reno in 2015. His Double-A walk rate of 16.1% was the high watermark for any portion of a season in which he played more than 8 games. He maintained his approach in Triple-A, carrying over equally impressive BB and K ratios.

Now, although the walks have tapered off, O’Brien is still limiting his strikeouts—relatively speaking—to around 30%. Although FanGraphs lacks the technology to pitch track plate discipline in the minors, we can see that O’Brien’s swing tendencies are much improved from his last stint in the Major Leagues.

Peter O’Brien Swing Tendencies

Year Team Games PA Swing % O-Swing % Swinging Strike %
Year Team Games PA Swing % O-Swing % Swinging Strike %
2015 Diamondbacks 8 12 46.7% 35.7% 28.9%
2016 Diamondbacks 28 67 62.4% 45.8% 24.3%
2018 Marlins 19 60 46.5% 26.7% 13.6%
Fangraphs.com

Logically, his reward for increased patience at the dish has been higher on-base percentage and better overall hitting metrics. Sample size is all over the place, and probably too small to really make a judgment about whether he has made the necessary adjustments, but compared to his biggest sample in 2016—and judging off of his K and BB rates in the minors this year—O’Brien may have finally figured something out.

Now that O’Brien is seeing the ball better, we can talk about what he’s really good at: mashing the ever-loving taters out of the baseball. Since coming to the Marlins, he has seized the top spot on the leaderboards in all batted ball, power hitting metrics.

Peter O’Brien Swing Metrics

Player Barrel % Hard Hit % xwOBA Avg. EV
Player Barrel % Hard Hit % xwOBA Avg. EV
Peter O'Brien 14.70% 52.90% .394 91.2 MPH
Giancarlo Stanton 14.60% 51.10% .349 93.7 MPH
Justin Bour 10.40% 38.90% .350 88.8 MPH
Derek Dietrich 6.20% 37.70% .328 86.4 MPH
Baseball Savant

I’m not going to say that Peter O’Brien hits the ball harder than Giancarlo Stanton, but I’ll let the numbers speak for themselves. Again, again, again, I have to caveat for sample size because it’s unlikely that anyone sustains the ability to hit the ball hard on a seasonal basis like G does. Comparing O’Brien’s 19 games to the totals of Stanton, Justin Bour, and Derek Dietrich is unfair. But this certainly sheds light on Don Mattingly’s rationale for giving O’Brien such consistent reps at the end of this season.

With relatively no competition below him (no disrespect to 31 year-old Eric Campbell’s impressive season in Triple-A) and no one on the active roster to split time with, who is keeping Peter O’Brien from re-making his home in Miami next season?

For one, his separated-at-birth twin brother Garrett Cooper. Cooper, another first base/outfield prospect jettisoned by the New York Yankees, is also over 6’4” and a righty bat. Cooper was hampered by injuries this year, logging playing time in just 14 games. He had surgery on his ailing wrist at the end of August; but if he can recover in the offseason, Mattingly will have a decision to make between essentially two identical players.

Why not keep both, especially if O’Brien picks up where he left off this year? Why not put one at first, and the other in the outfield? While that is an option, the Marlins will otherwise have incredible depth on a string between third base, first base, and the outfield. Martín Prado has the biggest paycheck of his contract coming next year at a whopping $15 million. Barring retirement, for one last time, the Marlins will have to find a spot for him on the field. Given the nature of his injuries, that spot may be at first base now.

Even if Prado played third base, that would just force Brian Anderson to move back to right field, presumably where Cooper or O’Brien would be stashed. That leaves two spots for any combination of Lewis Brinson, Magneuris Sierra, Derek Dietrich, Austin Dean, Monte Harrison, and any of the other September call-ups that have made splashes with the Fish this season. With the exception of Dietrich, salary is negligible, because all will be under total team control for the next two years.

So there will definitely be competition for a spot next year. With that said, O’Brien must feel confident in his abilities. What was once viewed as a salvage project for as many five different organizations has now cleaned up for a Major League team in nine consecutive games. Getting a chance to prove yourself is one thing; actually doing it takes a lot of grit. Make no mistake about it, Peter O’Brien has willed himself into the conversation for next year, and may very well be playing ball in Miami once again come next April.


Statistics courtesy of Fangraphs.com and Baseball Savant