The case for Nationals' outfielder Steven Souza, Jr.

On Sunday, we learned that the Nationals will be calling up Steven Souza, Jr. as Nate McLouth is expected to be placed on the disabled list. This article was in the works already. While I'm going to change some things to reflect the roster move that called Souza up, I'm going to stick with the general premise that it was probably about time the Nats called him up anyway.

The July 31 non-waiver trade deadline has come and gone. The Nats did make a move at the deadline, acquiring Asdrubal Cabrera from Cleveland for slugging infielder Zach Walters. They did not get the bullpen arm that they claimed to be seeking. Adam Kilgore of the Washington Post told us why the Nationals didn't make that second move.

The Nationals tried to make more than one trade Thursday, according to a person familiar with the Nationals’ dealings. In the weeks leading up to the deadline, the Nationals focused on adding a relief pitcher. They made several offers to teams for a handful of relievers in the final minutes. They would have landed one, the person said, but they did not want to part with Class AAA Syracuse outfielder Steven Souza.

I'll start making my case by saying that I'm glad the Nationals held onto Souza at the deadline. Had they not been able to get Cabrera relatively as cheaply as they did, I would have been OK with seeing him traded for a second baseman who could have filled the position beyond this season. Given the volatility of relievers, it would have been disappointing to see him traded to upgrade the sixth or seventh man in the bullpen. That's a discussion for another time and place, though. Let's stick to the topic at hand, shall we? First, some background on Souza for those of you who are unfamiliar with him.

A little background

Souza was drafted as a toolsy Shortstop out of Cascade High School in the Seattle suburb of Everett, WA. It didn't really take the Nationals long to move him off of SS, as he's played just 64 of his 730 (mostly in 2009) games there since turning professional. The Nationals tried to keep him on the infield, using him primarily at 3b from 2007-2010. He spent most of the 2011 season at 1b before moving to the outfield full time in 2012. He's remained in the outfield ever since. He's primarily played RF, but he has spent some time in CF in each of the past three seasons.

Souza's path to minor league stardom was littered with trials. From 2007-2011, his best full season line was .228/.360/.367. Souza was also suspended for 50 games in 2010 for testing positive for Concerta, a prescription ADHD medication on the banned substance list. While this is generally something that would lead some to question his character, Souza credits that experience with turning his life around, as well as his baseball career.

Souza began to show improvement in 2011, particularly with his strike zone judgment. He always seemed comfortable working a walk early in his career. In 2011, his walk rate nearly doubled from the previous season.  While he still wasn't hitting for average (.228), his .360 OBP was a significant bump over anything he'd done in his past.

The Breakout

In 2012, after having played three different infield positions in his four seasons in the Nationals' system, Souza moved to the outfield. This is where he really took off!  Prior to 2012, Souza had never hit higher than .237 over the course of a full season. He'd never had an OBP above .360. He'd never slugged higher than .432. How has he done since the beginning of the 2012 season?

• Souza turned in a .297/.366/.572 line between Hagerstown and Potomac in 2012. He also doubled his previous career best with 23 HR.
• He'd follow that season up with his first taste of the high minors, dominating the Eastern League in 2013 with a .300/.396/.557 line at Harrisburg. While he fell 8 HR shy of his 2012 production, he missed quite a bit of time with a shoulder injury.
• After jumping up another level to Syracuse in 2014, Souza has responded by leading the league in all three triple slash categories (.352/.434/599) and annihilating any contenders with a 182 wRC+*. He's continued to show immense power, bashing 18 HR in 385 PA and a .248 ISO.
• He runs, too. Souza has stolen 164 bases in 219 attempts (74.8%) throughout his minor league career. While his rate of success is league average, it's yet another one of those tools that led to the Nationals selecting him in 2007.

Since we're using an advanced statistic, let's describe just how dominant this is. wRC+ is a statistic which determines how many runs a player creates per plate appearance using the linear weight wOBA. It adjusts for both park and league, and 100 is considered average. Souza leads the IL at 182 wRC+. Dan Johnson is a distant second with 143 wRC+. Think of it in terms of percentage. On a per plate appearance basis, Souza has created 182% of the runs that a league average player would.

Why should the Nationals call Souza up?

I'm going to do this in two segments. One is going to be agnostic of the Nationals' major league roster, since the organization should always be focused on the long term development of the player. The other is going to focus on the Nationals' bench and how the big league club could use him. Let's start with Souza, since his development is the key factor here.

Is it likely to stunt Souza's development by calling him up?

We always want to see a player who would be considered a prospect getting as many at bats as possible. Players don't simply mature because they're advanced a level in the system. They mature because of repetition... facing those tougher pitchers as they advance through the system. Even in cases where a player seems to have mastered a level (as Souza's AAA statistics would indicate he has), it can make sense to keep him there if there isn't an opportunity for him to get regular at bats at the next level.

I'm not sure that there are a lot of at bats available to Souza right now. The Nationals are in win now mode and are set at all three outfield positions (and first base). Based on his absolute destruction of the International League, it's becoming clear that he doesn't have a lot to prove at the minor league level. It would be one thing if he were a hitter having a really good season. It's another for him to be producing at a level as high as 182% of the league average.... again, 39% higher than anyone else in the league. While this is still only about two-thirds of a season at AAA (not a huge sample size, but not small either), Souza seems more likely to improve by facing better pitchers at the highest level... even if those at bats are more scarce.

But wait... there's more!

Career Arc

Let's start by pointing you to another article by J.C. Bradbury in the Baseball Prospectus Archives. This article was written in 2010, but it still holds pretty true. I encourage you to read Bradbury's entire piece, but here are some of the highlights.

Bradbury's conclusion:

I began my investigation into how baseball players age in order to address some potential problems with past studies. It turns out that after correcting for those flaws that the peak age of baseball players appears to be around 29, and possibly 30 for hitters in modern times. Of course, some players will peak earlier and others later, but this is a general benchmark.

Bradbury also makes reference a Bill James essay "Finding The Prime":

James used his "Value Approximation Method" (VAM) to measure player performance by aggregating individual VAM ratings of players by age. He found that the player-age of 27 had the highest total performance of any other age and concluded, "If you must assign a five-year peak period to all players regardless of description, the best shot would be 25 to 29."

Finally, let's skip to James' conclusion which he references at the end of the article:

Good hitters stay around, weak hitters don't. Most players are declining by age 30; all players are declining by age 33. There are difference in rates of decline, but those differences are far less significant for the assessment of future value than are the differing levels of ability (James, 1982, p. 205).

Here's the chart showing the findings of Bradbury's study. We'll see that these players tended to trend upwards until their age 29 season. We then see a moderate decline at age 30 that gradually erodes as the player ages.

Of course, there are other factors that apply. While James' findings are that a player peaks from 25 to 29 (age 27, most likely) and Bradbury found it be 29, it's probable that the findings aren't all related to when their physical ability is at its peak. Most players that stick as big league regulars reach the majors at least a few years before they have their peak season. That experience and comfort level against their level of competition factors in as well. Let's call it the intersection of peak physical ability and experience.

Applying this to Souza

Souza has played 730 games in the minors at this point. While just 166 of those games have been played above A ball, he's now 25 years old. In the typical arc of a baseball player's career, Souza should be approaching his peak.  While the Nats may prefer to let him remain in AAA for a full season before calling him up to the majors for good, there's a fairly high likelihood that Souza is as physically gifted as he's ever going to get at this moment.

In the cases of younger players, I understand the reluctance quite a bit more. If we were talking about a 22 or 23 year old, the Nats would have two issues facing them that they aren't facing as much with Souza:

• A projected growth in physical talent and abilities. Regardless of whether he actually is at his physical peak or not, he doesn't have the room for physical growth that a younger player would.
• Service clock issues. Depending upon service time manipulation within a player's rookie season (this is commonplace), the club that owns his rights will have him for six seasons worth of service time from when they call him up. In the majority of cases, this actually ends up being seven seasons, as a player must have six full seasons worth of service time before they can become a free agent. Quite frequently, this is a determining factor in whether a club takes a rookie north from Spring Training. If they wait until late April, they'll "gain" a year of club control before that player can become a free agent.

That Peak May Not Last Long

The Bench

Well... Souza's getting the call.  How should the Nats handle him?