Going Deep: Peter Alonso is Ready to Hit Home Runs and Break Radar Guns

Nick explores what makes Peter Alonso such a special hitter and why fans should be excited for his 2019 MLB debut.

New York Mets first base prospect Peter Alonso developed quite the following over the years.  The Tampa, FL native and 2016 second round pick drew accolades in prospect circles in 2017 by displaying a unique blend of power and plate discipline in the low-level minors. Alonso then proceeded to launch into the mainstream with a monstrous 2018 season, leading the minor leagues in home runs and setting social media abuzz with particularly impressive performances at the Futures Game and Arizona Fall League. Alonso’s 36 home runs in 2018 were impressive in their own right, however, it’s his well-rounded approach at the plate, highlighted by strong batting averages and reasonable strikeout rates, that makes his MLB potential particularly exciting.

Despite Alonso’s numerous achievements in 2018, the Mets deprived the recently turned 24-year old of a call-up to the big league roster last September. While the humble and charismatic Alonso took it in stride, he clearly has his sights set on locking down the Mets starting first baseman job in spring training and making a major league impact out of the gate. Freshly minted Mets GM Brodie Van Wagenen, who has taken a shine to Alonso, did his part to make that a reality by non-tendering utility man Wilmer Flores and trading 1B/OF Jay Bruce, the incumbents at the position.

Alonso will face some headwinds as a defensively challenged first baseman in the National League. Moreover, while his minor league statistics point to a player with good plate discipline, there are some holes in his swing and approach that could be exposed by MLB-quality pitching. However, the power potential is near 80-grade, and his ability to spray the ball to all fields should make him a dynamic enough hitter to withstand the inevitable increase in strikeouts. With a grasp on a full-time MLB at bats within reach, Peter Alonso should be on everyone’s radar heading into 2019, and I wouldn’t be surprised to see a 260 average with a 30-home run and 90-RBI stat line in his rookie year.


What’s all the fuss about?


Before delving into why Alonso is deserving of your attention, let’s address why he might be overlooked and undervalued from both real life and fantasy perspectives heading into 2019. Alonso, standing at a robust 6’3″, 230lbs and swinging from the right side of the plate, looks the part of the standard burly, power-hitting first baseman. This archetype once cherished in the late 90s and early 00s is becoming a relic of a bygone era at the MLB level. As a result, unearthing a plodding defensively challenged first base prospect isn’t exactly like finding a unicorn. These players exist in spades throughout the minors and majors and the demand for their services is declining. If you’re skeptical just ask former Tampa Ray CJ Cron, a fellow righty-righty first baseman who was unceremoniously cut in November after posting a 30 HR season that was worth a 122 wRC+ and 2.1 WAR. Cron quickly found work with the Minnesota Twins, but on a meager one-year, $4.8 million contract that represents a 72% discount from his 2018 fWAR value of $17.1 million.

For these reasons, Peter Alonso is fighting an uphill battle in the baseball court of public opinion. Prognosticators will discount his impressive minor league numbers without spending the time to fully appreciate the magnitude of the performance. Standard prospect lists tend to rank him lower than expected due to his position and defensive deficiencies. However, the enterprising baseball mind and fantasy manager should remember that for these same reasons, Phillies’ slugger 1B/OF Rhys Hoskins was a relative unknown prior to his MLB promotion despite putting up otherworldly minor league numbers. We all know how that turned out.



What matters isn’t just that Alonso has power. It’s that his power is elite.  Some prospects with power potential exhibit it sporadically, perhaps based on the run scoring environment of the league, which calls into question the sustainability of that power against major league pitching. However, Alonso’s power is maddeningly consistent. From the pitcher-friendly Florida State League to the neutral run environment of the Eastern League to the bandboxes of the Pacific Coast League, Alonso has never posted below a .516 slugging percentage or .231 isolating slugging percentage (ISO) at any minor league level.

But there’s more to hitting than power. Toronto Blue Jays‘ prospect Cavan Biggio put up a similar ISO to Alonso in the AA Eastern League in 2018, yet he did so with a 26.3% strikeout rate. Generally, strikeout rates do not improve as a hitter progresses through levels, and it’s likely that Biggio will face a big challenge putting the ball in play in either AAA or the MLB in the near future. Alonso’s strikeout rate for the AA Binghamton Rumble Ponies last year was 18.3%, with an impressive 0.86 BB/K rate. The combination of this consistent plus-plus power with strikeout rates below 19.0% from low-A to AA decrease the risk that Alonso turns into a strikeout machine, like former Brewers slugger Chris Carter, when he hits the majors.

Alonso’s command of the strike zone is also exemplified by his ability to lay off bad pitches and work counts. Alonso saw an average of 4.2 pitches per plate appearances across both minor league levels in 2018, a patient approach comparable to the numbers attained by St. Louis first baseman Matt Carpenter and reigning AL MVP Mookie Betts at the MLB level. This measured technique allowed Alonso to post a 9.5% swinging strike rate in 2018, which is better than the minor league average of approximately 10.5%. Alonso’s above average performance in swinging strike rate is even more impressive when considering his power output. Generally, minor league hitters who have ISOs in the .250+ range tend to sacrifice plate discipline for power. St. Louis outfield prospect Tyler O’Neill, who posted a 15.7% swinging strike rate in 273 plate appearances with the AAA Memphis Red Birds, is a perfect example of this. O’Neill’s strikeout rate ballooned from 24.9% in AAA to 40.1% upon promotion to the Cardinals, indicating that his swing and miss tendencies in the minors were signaling potential hidden issues against major league pitching. Alonso’s impressive swinging strike rate is an indicator that he might have an easier time adapting when he hits the Show in 2019.



The cherry on top of Alonso’s hitting profile is his ability to hit for a decent batting average. Alonso is a career .290 hitter in the minors, a product of his passable strikeout rate but also of his ability to hit the ball hard to all fields. Alonso’s observed Statcast exit velocities put him in Aaron Judge-territory, while his 2018 minor league spray chart looks like something that should be in a modern art museum. Much of Alonso’s home run power comes to the pull-side, but a meaningful percentage of his hits came from the opposite field. The other plus to Alonso’s hitting technique is that, since his power so organically robust, he doesn’t need to rely on sky-high flyball rates to underwrite his offensive performance. Rhys Hoskins, a solid comp for Alonso, is one of the more extreme fly ball hitters in baseball history and his career 265 BABIP highlights a negative to that approach, since fly balls that don’t leave the yard typically convert to outs. As a result, it’s unlikely Hoskins ever ascends above a .250-.260 batting average. Alonso, with a career minor league BABIP of 319 and flyball rate of 42%, has a bit more dynamism in his approach and could be in the .270-.280 batting average range in the majors long-term.


How he does it


Understanding the statistical significance of Alonso’s minor league track record is important, however, a complete analysis also needs to delve into his hitting mechanics. Given that my skill set lies in data analysis and contextualization rather than scouting, I reached out to prospect guru Lance Brozdowski earlier this week for his take on Peter Alonso from a more traditional scouting perspective. The following opinions in this section are based on that conversation and featured significant input from Lance.

Alonso displays a fairly closed and compact stance that allows him to spring load to the ball upon arrival. Alonso’s hands sit close to his body and low to his chest, which, combined with the pullback in his hands upon pitch delivery, allows him to generate tremendous torque and subsequent bat speed at the point of attack. This approach, buffeted by Alonso’s natural strength, causes him to hit the ball with power in the air, on the ground and through left, right and center.


You’ll also notice that Alonso has a muted leg kick, which is increasingly atypical these days for young power hitters. Mashers like Braves third baseman Josh Donaldson and the aforementioned Hoskins use a pronounced leg kick to improve timing and power, yet plenty of players struggle with the additional complexity and movement this adds to their swing. Alonso already has a large amount of movement and torque coming from his upper body prior to the swing, so a noisy lower half wouldn’t necessarily be ideal for him.


Some points of concern


Despite the overall positive look of Alonso’s swings, there are some potential concerns for him going forward. The low set of Alonso’s hands might make him susceptible to high fastballs in the majors, as it’s harder for a hitter to swing up than down when cheesing the high cheese. This likely didn’t present a huge issue for him in the minors, but issues could crop up when he starts facing Max Scherzer-type spin rates and velocities in The Show.

There are some additional concerns about Alonso’s ability to hit high-spin breaking pitches, especially those placed low and away. Alonso’s strikeout rate ballooned from 18.3% in AA in 2018 to 25.9% in AAA, as craftier hurlers were able to get ahead easier and then fool him on 1-2 and 2-2 sliders and curveballs. Reports out of the Arizona Fall League echoed a similar sentiment, with Alonso’s 28 strikeouts ranking fourth in the league.

Alonso’s potential weak points on up-and-in fastballs and down-and-away breaking stuff point to a hitter that might struggle to translate his minor league strikeout rates to the next level. There are also some potential concerns about his gameplan at the plate. Alonso is a self-proclaimed “see the ball, hit the ball” hitter who doesn’t pay much credence to Statcast and advanced scouting reports.  This has clearly worked for him to date, as he can mash fastballs and minor league stuff with the best of them, however, he might need to bring more nuance to his at-bats in an NL East highlighted by stud Washington hurlers Scherzer, Patrick Corbin and Stephen Strasburg along with Philadelphia ace Aaron Nola. Unfortunately, the New York Mets, who have yet to join the sabermetric revolution with a mere three data analysts, are unlikely to bring advanced guidance from the top down, so it will be up to Alonso to sink or swim on his own.


It’s difficult to predict a player’s ability to adapt to a higher level of competition, particularly when that competition is MLB pitchers striking out batters at record rates. One data point that gives me confidence in Alonso’s ability to survive is the growth exhibited through his time in AAA last season. After thoroughly dominating the Eastern League, Alonso was called up and played his first game with AAA Las Vegas on June 16th. Alonso struggled out of the gate, posting a 28.1% strikeout rate, an unsightly 220 batting average and a mediocre 106 wRC+ in his first 167 PAs. But Alonso adapted, and over his last 30 games from August 1st onward, Alonso shaved the strikeout rate to 23.1% and produced a video game-like 308 / 388 / 726 triple slash line. While these splits represent a small sample of data, they point to Alonso’s ability to face adversity and make the adjustments necessary to succeed.


The Statcast king


No article on Peter Alonso would be complete without telling of his Statcast exploits. Put simply, Alonso murders the baseball. In the July 2018 MLB Futures Game, Alonso knocked a towering two-run home run in the seventh inning that measured 113 MPH off the bat. What was particularly impressive about this 113 MPH home run was that it came at a 46-degree launch angle, a combination never measured before in Statcast history (Statcast has never even tracked a home run hit harder than 110 MPH at an angle higher than 45 degrees). Futures Game Team USA Manager Torii Hunter was clearly impressed with Alonso’s showing and commented, “That’s unbelievable power; I saw Mark McGuire hit like that.” Pretty impressive company.

Then came the Arizona Fall League in October and November 2018. Fortunately, Salt River Fields, one of the six fields used in the AFL, is outfitted with Statcast technology. The hardest hit ball of the tournament came on a groundout by Indians prospect OF Daniel Johnson at 116.4 MPH, but Alonso clocked in second with a 116.3 MPH double. One of his six fall league home runs came in at 113.8 MPH, which was good enough for the sixth hardest hit ball. Alonso was the only player with two batted balls in the top 10.



Further adding to the legend, Alonso also hit a home run off a 103 MPH fastball thrown by Blue Jays pitching prospect Nate Pearson. No player in the MLB Statcast era has ever hit a home run off a pitch that fast, with the closest being a Rafael Devers homer off a 102.8 MPH RP Aroldis Chapman pitch in 2017.

Alonso’s Statcast performance provides mainly anecdotal evidence of his skill, but the ability to hit pitches on the extreme end of the velocity spectrum provides additional support for the unique nature of Alonso’s hitting potential.

Nick Gerli

Nick is a Boston-based baseball nerd originally hailing from New York. He is passionate about baseball (duh), finance and heavy metal music. In the warmer months you can often find him wandering around Fenway Park in a Jacoby Ellsbury Yankees shirt. @nickgerliPL

5 responses to “Going Deep: Peter Alonso is Ready to Hit Home Runs and Break Radar Guns”

  1. Bill says:

    Great article. I get all the metric stuff. I also believe that the Mets have enough offense in front and in back of him to get him a significant amount of juicy pitches to hit,unless they walk him.

    • Nick Gerli says:

      Thanks for the response!

      Mets might have a sneaky good offense this year, especially if Conforto’s shoulder is truly back and Nimmo keeps it up.

  2. Robert says:

    Great read, Nick. Does a good job backing my blind optimism as a Mets fan.

  3. HJ Upton says:

    Thanks for the article, Nick! I drafted him in my dynasty league. I think he’s going to be a stud. Might be worth bumping this article when he wins job out of spring training.

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