When the Royals signed Melky Cabrera this offseason, I was confused. They had Mitch Maier, Gregor Blanco, and Jarrod Dyson all ready to compete for the centerfield job, and then traded for Lorenzo Cain to make things more complicated. Cabrera was coming off a miserable season for the Braves; he was a full win below replacement level, thanks to a wOBA of .294 and a UZR/150 of -18.9. The Melkman, however, has rewarded Dayton's faith. He currently has a .286/.324/.454 triple slash line, good for a wOBA of .343. His fielding numbers are substantially better this season as well, his UZR/150 is only -1.8. Combine these with above-average baserunning numbers (positive for the first time since 2006), and Melky has been worth a surprising 2.6 WAR for Kansas City.
With the season a little over halfway done, it's tempting to assume Melky will be worth 2.6 WAR in the second-half of the season, or close to it. I did a poor job by making this assumption with Wilson Betemit, and was corrected for it. Current WAR is not necessarily predictive of future WAR. ZiPS project Melky to have a triple slash of .275/.326/.416, good for a wOBA of .325. The projection system believes that Melky will be unable to sustain his ISO, which is high in large part due to an 11% HR/FB ratio. His career average is 6.8%, so it is reasonable to expect some regression. If we use the ZiPS estimate for how Melky will perform the rest of the season, he will roughly be worth .6 hitting WAR. If you think he will hit better than ZiPS projects, somewhere around a wOBA of .335, Melky will be worth roughly 1.1 hitting WAR. If you are very optimistic and think Melky will continue to post a wOBA of .343, he will be worth 1.6 hitting WAR.
Projecting Cabrera's fielding wins is considerably more difficult, since we are not sure if he will play centerfield, a corner outfield spot, or a mixture of both. Melky has played the vast majority of innings this season in centerfield, and the numbers say he has been slightly below-average in center. Theoretically, contenders who are looking for an upgrade in center would be interested in Melky. There is one small problem; most contending teams do not need a centerfielder. The Yankees, Red Sox, Phillies, Diamondbacks, and Pirates(!) are all in contention and have centerfielders performing better than Cabrera. The Rockies, Angels, Reds and Cardinals all have young centerfielders that are close to the Melkman in WAR. That leaves the Rangers, White Sox, Tigers, Braves, Indians, Rays, and Mariners(!) as teams in contention. The Rangers have Josh Hamilton, so I doubt they will want an upgrade. The Rays, Tigers, and Indians all have young centerfielders (B.J Upton, Austin Jackson, and Michael Brantley, respectively) that are not likely to be replaced. Alex Rios has been horrendous for the White Sox this season, but they are paying him a lot of money, so one would expect them to stick with him.
That leaves the Braves, Mariners, and maybe the White Sox (Kenny Williams is unpredictable) as teams who might trade for Melky and play him in center. The Braves had a rough season with Cabrera last year; I doubt they would want to trade for him, but you never know. If Melky was traded to a team that promised him the centerfield job, we can reasonably guess that he would be worth roughly .5 fielding WAR, the slightly below-average defense would be offset by the positional adjustment. So if a team trades for Melky and plans on using him everyday in centerfield, we can project Melky to have somethwere between 1.1-2.1 WAR the rest of the season. For purposes of this article, I will assume 1.6 WAR for Melky if he is traded to be a centerfielder.
Melky may not be traded to a team that wants to play him exclusively in centerfield; Cabrera would be an upgrade as a corner outfielder for many contending clubs as well. The Mariners, Phillies, White Sox, and Angels all have below-replacement outfielders in leftfield; the Mariners and Red Sox also have had below-replacement level performances in rightfield. The Angels, Phillies, and Reds also could use better performances out of their rightfielders. Not all of these teams will be interested in upgrading (I can't imagine the Reds benching Jay Bruce), but there are teams that might want Melky to be a corner outfielder, or play multiple outfield positions. If Melky plays most of his innings in the corner, I would predict for him to have zero fielding wins. Although he would be a better fielder, the positional adjustment for right or leftfield compared to centerfield would render it negligent. So if Melky plays a corner outfield position, I would guess he would be worth around 0 .6-1.6 WAR. For purposes of this article, I will assume 1.1 WAR for Melky if he is traded to be a corner outfielder.
The big leagues clubs have roughly valued wins at 5 million dollars per win this season, and Melky has around 600K dollars left on his contract (he also has 250K worth of incentives I hope the Royals would be willing to pay). That means Cabrera would be worth 4.9 million to 7.4 million dollars in excess value the rest of the season if the Royals do not pay his contact; he would be worth 5.5 million to 8 million dollars in excess value if the Royals pay his contract. According to Victor Wang, a grade B hitter is worth roughly 5.5 million dollars, and a grade B pitcher is worth around 7.3 million dollars. A grade B prospect is still a good prospect; John Sickels rated Christopher Dwyer, Brett Eibner, and Christian Colon as Grade B prospects. So if the Royals decide to trade Melky, he could potentially bring back another team's top-ten talent.
The Melkman may also be viewed as more than a half-season rental, he will be eligible for arbitration next season. I don't know, however, how much this will help the Royals. Teams should know that Cain is ready for a call-up, and that the Royals would like to move Cabrera; this lack of leverage may cancel out the bonus of Melky being cost-controlled next season. If a team is looking for more than a rental (Mariners?) they may be willing to part with more prospects, or one more valuable prospect. For the sake of this article, I decided to estimate conservatively and treat Melky as a half-season rental.
There have been a few outfielders that have been traded in recent years that compare roughly to how Melky is performing this season. Nyjer Morgan, Nate McLouth, and Xavier Nady were all traded by the Pirates, and those trades have some similarities. Morgan and Nady were packaged with relievers, and none of them brought back one B prospect; instead, it looks they returned a few C+ pitchers or hitters, or a B- player with one C prospect. If the Royals follow this path, they may bring back multiple prospects who aren't as highly rated as one B prospect, in order to spread out the risk among multiple prospects.
Overall, Melky has been a pleasant surprise for the Royals this season, and Dayton Moore might be rewarded with some more solid prospects in exchange for Cabrera's services. I still don't know if I would have signed him last off season, but it's hard to argue Moore made a mistake by signing the outfielder. I would imagine there is a large chance Melky is traded, somewhere around 90%; he is young, cheap, and can play all three outfield positions. If Cabrera is not traded, I imagine most Royals fans would be very disappointed; Melky has played well, but he doesn't represent the "youth movement," even though he is not much older than Cain or Dyson. Dayton made a good gamble by signing Cabrera this offseason, and hopefully reaps his rewards in the next month.