The PECOTA projection system used by Baseball Prospectus works in part by figuring out which players have had similar career paths to each other, and then using those similar players to project future performance. After the Rays claimed Daniel Nava off waivers from the Red Sox, I flipped over to look at the similarity scores, and one in particular caught my eye.
Through their age-31 seasons, the fifth-most similar career path to Danial Nava was that of David DeJesus.
DeJesus, of course, played another year of slightly-above-average baseball in his age-32 season, and then was acquired in a waiver trade during his age-33 season by the Rays. Nava hurt his thumb in his age-32 season, played poorly (in limited plate appearances) after returning form the DL, and then was acquired off waivers by the Rays.
The comparison is pretty good. Both of them are outfielders who have spent some time in center field, but who were a better fit in a corner by the time they got to the Rays (although it should be made clear that DeJesus was the better fielder—he was well above average in a corner during his prime, and Nava is probably much more closer to average). Both of them carry wide platoon splits, hitting right-handed pitching much much better than they do left-handed pitching. Both of them are known for their discipline and understanding of the strike zone, as well as a small but real amount of pop (which the Rays will hope hasn't completely left Nava, although it hasn't shown itself for two years). Both of them are thought of as good clubhouse presences.
Here is a graph of their careers:
Of course, it's not identical. DeJesus's career has been both longer and better, while Nava—not offered a scholarship out of high school, not drafted, and having to work through the independent leagues—got a pretty late start on his.
Still, it's interesting that the Rays just traded DeJesus, and then swooped in to pick up one of the most similar guys on the market.
The point here is probably not that the Rays wanted to swap DeJesus for a younger, lesser version of himself. When they traded DDJ, they didn't know Nava was going to become available. The lesson is in the other side of each move, and the value gained by the Rays in the transaction.
When the Rays first acquired DDJ, they did so by sending the Nationals a player to be named later, which turned into lightly-regarded pitcher Matt Spann (who, it should be noted, was just promoted to triple-A, although without impressive stats). When they sold DeJesus, they received Eduar Lopez, a young pitcher ranked 22nd in the Angels system by Baseball America. In either case, the Rays felt they were making a profit.
Now comes along Nava, a player with two years of team control left whose career path puts him at a similar place to where DeJesus was when the Rays traded Spann for him. This time, the cost was just a few dollars out of owner Stuart Sternberg's pocket book, so the Rays front office acted consistently and grabbed the asset.
Not every 33 year old continues to hit, especially when injuries are thrown into the mixer, but if Nava can continue to follow DeJesus's career, he will easily justify the cost the Rays have paid to get him.