We Blew It

OK, everybody who thought that last year's trade of Alfonso Soriano for Brad Wilkerson was a good deal for the Rangers, hold up your hand. C'mon, get 'em up—don't worry, you're not alone. My own mitt is sheepishly raised. When the trade was made about a year ago, many commentators cited the trade as another example of Washington general manager Jim Bowden's ineptitude. I don't want to single out any particular blogger; if you want to go back and read individual posts, it's easy to find them (Google "+Soriano +Wilkerson +trade" for a sampling). Suffice to say that most bloggers thought Bowden had made a major mistake—and it wasn't even close.

I didn't actually write anything about the trade, but I nodded knowingly while reading those pieces and was totally in agreement with my sabermetrically inclined colleagues. Now it's time to admit the mistake.

The Trade

First some background: in December of 2005, the Nationals and Rangers made a four-player trade: the Nats obtained Soriano while the Rangers got Wilkerson, fourth-outfielder Terrmel Sledge and a minor league pitcher named Armando Galarraga. Sledge was 28 years old, had missed the previous season with a torn hamstring, and even when he played he wasn't very good. A month later he was a throw-in in the big trade with San Diego, which sent Adrian Gonzalez and Chris Young to the Pads in exchange for Akinori Otsuka and Adam Eaton. Galarraga, at the time, was a 24-year-old mid-to-low-level prospect, who had struggled in a half-season at the Double-A level. The trade involved money issues as well: Soriano was set to make about $10 million, while Wilkerson was making $4 million. Also, Soriano was to be a free-agent in 2007, while Wilkerson would remain under the Rangers' control for two full seasons.

So, the deal was a bit complex, but let's just break it down as Soriano vs. Wilkerson. If you go back and read the commentary at the time, just about everybody was evaluating the trade by comparing these two players straight up. That makes sense in a way, as you often hear the "winner" of a trade is the team who gets the best player in the deal. So who got the best player in this deal?

Here's what the two players ended up doing in 2006:

+-----------+------+------+------+----+------+------+------+-------+-------+-------+
| Player    | PA   | R    | H    | HR | RBI  | SB   | CS   | AVG   | OBP   | SLG   |
+-----------+------+------+------+----+------+------+------+-------+-------+-------+
| Soriano   |  726 |  119 |  179 | 46 |   95 |   41 |   17 | 0.277 | 0.351 | 0.560 |
| Wilkerson |  363 |   56 |   71 | 15 |   44 |    3 |    2 | 0.222 | 0.306 | 0.422 |
+-----------+------+------+------+----+------+------+------+-------+-------+-------+

The Almighty Walk

Well, one thing that I think happened is a lot of saber-minded folks don't really like players like Alfonso Soriano. Why? Because they don't walk much and hence they don't excel in getting on base. On-base-percentage is justly regarded as the single most important contribution to run scoring and, at the time of the trade, Wilkerson had a big edge over Soriano in career OBP: .365 to .320. But, as the saying goes, there is more than one way to skin a cat, or produce on a ball field. Soriano had a big edge of his own: the ability to drive the ball for extra bases. Soriano's career slugging percentage (through 2005) topped Wilkerson's, .500 to .452. Now, it's generally accepted that a point of OBP is more valuable than a point of SLG, so perhaps Wilkerson has an edge here due to his higher OBP. But, Soriano had other advantages over Wilkerson: his speed and the fact that he played a premium defensive position.

Through 2005, Soriano had stolen 169 bases at an 80% success rate, while Wilkerson had swiped only 43 bases at a decidedly uninspiring success rate of 55%. And, although Soriano was generally considered a poor second baseman, there is value in getting a big bat in the lineup at a traditionally weak-hitting position. Now, whether Soriano's bat was actually compensating for his defense—that is not an easy question to answer with any degree of certainty. But we can try. Using one defensive metric, Baseball Prospectus' FRAA (that's Fielding Runs Above Average), Soriano averaged -9 runs for 2001-2005. The offensive difference between an average-hitting second baseman and an average-hitting corner outfielder is generally larger than nine runs, so despite the weak glove, Soriano's defensive position is a net gain. Wilkerson is an OF/1B type.

So, Wilkerson looked to be a slightly better hitter perhaps, but one could argue that Soriano compensated with his speed and by playing a premium position on defense. In any case, it's seems hard to make the case, at this point, that Wilkerson was clearly the better player, which is what we were saying a year ago.

On The Road

I haven't mentioned park effects at at all and the fact that the trade had Soriano moving from a hitter's park in Texas to a pitcher's park in Washington had many predicting hard times for Alfonso in 2006. Some pundits at the time sought to shed light on the home park issue by comparing only the road stats of the players. And when you do that, a red flag certainly goes up for Soriano:

Home/Road Splits, 2004-2005
                Home             Road
Soriano    .316/.357/.593   .234/.278/.409
Wilkerson  .250/.371/.456   .253/.355/.449

For one, or even several, years of data only, using road stats only is a HORRIBLE method of estimating player neutral performance or talent. Absolutely horrible. To simply ignore half of a player's performance because you are worried about properly neutralizing those home stats (which is admittedly problematic) is the epitome of throwing out the baby with the bath water.

The Perils of Park Factors

OK, so considering a player's road stats while tossing his home stats out the window is not the way to go. A better way is to apply park adjustments to a player's complete stats to try to take the effect of the home park into account. This is actually a tricky subject, because there are different park factors on the market and if you apply one blindly, you may not be doing the right thing or even doing what you want.

Park factors in their basic form are fairly simple: you calculate the number of runs scored in, for example, Rangers home games and divide that by the runs scored in Rangers away games. That gives a reasonable result, but you can improve things if you actually consider the number of innings played in the home and away games: the innings count can vary quite a bit, especially for teams with very good home records: the winning team does not usually bat in the bottom of the ninth. There is also quite a bit of statistical fluctuation in park factors—analysts attempt to minimize those by 1) using regression to the mean and/or 2) combining data over a period of several years.

OK, I don't want to give a treatise on park factors, but I wanted to point out that they aren't as simple as they seem. I'm wondering if some confusion about park factors contributed to the pessimistic judgments of Soriano a year ago. Ameriquest Field in Texas is rightly regarded as a hitter's park, but it's not Coors Field by any stretch of the imagination. The five-year park adjustment for Ameriquest from 2001-2005 is 107 (without any regression), which is a good hitter's park, but we're talking about a 7% correction to a Ranger's stat line. This can in no way explain Soriano's home/road stats that we saw above.

Soriano's new park in Washington, RFK Stadium, had a park adjustment of 93 in 2005, the only year of data available for that park. I'm using Baseball Reference as a source for park adjustments, because I'm guessing that many people do the same. That's a good pitcher's park, but it's only based on one year of data, and hence is "polluted" by statistical noise. In fact, the park adjustment for RFK in 2006 was much higher, at 97. Where the number settles down is anybody's guess, but the point is that putting too much faith in a one year park factor is rather dangerous.

What about Wilkerson's home parks? Wilkerson had been a regular from 2002-2005 at the time of the trade and his one year park adjustments from that period are 101, 118, 95 and 93. The last number is the already-mentioned RFK 2005 value and the 2003-2004 numbers (118 and 95) represent "combined" park factors when the Nats played a bunch of home games in Puerto Rico. I'm rather skeptical of these Monteal/Puerto Rico park adjustments, especially since the two years show such a wide variation—a 23% change in park adjustment in one year is very unusual. I'm not at all confident that those games in Puerto Rico did not add in even more "pollution" to the one-year numbers. To accentuate this issue, Wilkerson had his very best season in 2004, with an OPS of .892. The low park adjustment for 2004 gives him on OPS+ of 128, which to me looks like it's overestimated.

A last note on park factors: I actually don't like the Baseball Reference park factors, mainly because (since 1999) they are based on only a year's worth of data (although the description of the park factor calculation at bb-ref.com says the park factor is based on 3 years worth of data—this is not correct). Here at the Hardball Times we use the park factors calculated by the sabermetrician known as USPatriot. USPat uses five years of data (when available) and also includes some regression to the mean. His results can differ quite a bit from the Baseball Reference numbers: for example the 118, 95 that bb-ref.com finds for Montreal in 2003-2004 are calculated by USPat to be 102 and 104. Note that using this improved park factor, Wilkerson's 2004 OPS+ goes from 128 to 117. Oops.

Age and Durability

Is there any reason to think that Soriano's projection going forward from 2005 should have been downgraded due to age and/or durability issues? I don't think so. Soriano's 2006 seasonal age was 29, Wilkerson is one year younger. It's true that Soriano was past the canonical peak age of 27, but the downward slope of the aging curve is very shallow at age 29 and projecting a steep dropoff due to age would have been foolhardy. Furthermore, research has shown that fast, athletic players like Soriano tend to age better than average.

On the question of durability, there's not much difference between Soriano and Wilkerson, at least there wasn't before the 2006 season. From 2001-2005 Soriano was very durable, averaging 154 games per season. Wilkerson was pretty tough, as well, averaging 152 games per season from 2002-2005.

The Last Word

Just to recap—it seems to me that the rush to condemn Jim Bowden for the Soriano-Wilkerson trade a year ago may have been a bit hasty and overly hostile. I think a careful analysis at the time would have shown Soriano and Wilkerson to be players of comparable ability. I'm speculating that a superficial treatment of park effects and perhaps an ingrained prejudice against players with below-average plate discipline led many commentators astray when evaluating this trade.

Or maybe not. Maybe Wilkerson really was and still is a better player than Soriano. Perhaps 2006 was just an aberration—a career-year for Soriano and just an injury-marred bad-luck campaign for Wilkerson. It may be that another year or two of data will show Wilkerson's superiority. Perhaps, but I don't think so. I think we just blew this one.