On Tuesday night, the White Sox and Diamondbacks agreed to swap Arizona RP Tony Pena for Chicago White Sox 1B prospect Brandon Allen. The Diamondbacks, at 35-49 and a .04% chance to make the playoffs (as of Tuesday), are firmly entrenched as sellers in this year's trade market. This deal seems to show that the Chicago White Sox, on the other hand, are poised to buy, at 42-40 and with roughly 30% playoff odds. Pena has had a slightly rough year by traditional standards for the D-Backs, with a 4.24 ERA in 34 innings as setup man for Chad Qualls. Still, Pena's relatively high ERA did not dissuade White Sox GM Kenny Williams from pulling the trigger on this move. Digging deeper, Pena's 2.36 K/BB and 0.79 HR/9 have resulted in a solid 3.72 FIP, between his career average of 4.01 and last year's 3.42. Pena's good pitching in high leverage innings combined with the ability to shoulder a relatively heavy load (157 IP between 2007-2008) have made Pena worth 2.2 wins since 2007 (including 2009 so far).
Pena will replace Jimmy Gobble in the White Sox bullpen. Gobble's 7.50 ERA was supported by an equally (for all intents and purposes) bad 6.87 FIP. Gobble never was a stud pitcher by any means and has always been susceptible to the home run, with no full season HR/9 below 1.00. Finally, in 2008 and 2009, the other shoe dropped, and Gobble's walk rate rose to a point at which he is no longer a major league pitcher. If Pena either keeps pitching at his current pace or hits his ZiPS projection of a 3.53 FIP, Pena figures to be a .4 to .5 win upgrade this year. Pena has still not yet entered arbitration, and will be a cheap asset for the next 3 years. Although relievers are volatile, Pena seems to be a safe bet for anywhere in the 0.5 to 1.0 WAR range, with the potential for more if he eventually moves to a closer role. As long as his contract is in the 1.5-2.5 million dollar range, Pena is a decent, albeit not great, asset to a major league club.
Brandon Allen was the 4th rated prospect by John Sickels in the White Sox minor league system entering the year, behind Gordon Beckham, Aaron Poreda, and Tyler Flowers. Both Beckham and Poreda have already seen significant time with the Major League club. Allen has struggled in a very short stint at AAA, but not much can be learned from that. In roughly 275 AA PAs this year, Allen showed decent power with a .182 ISO and good on-base ability, with a .369 OBP supported by a .083 IsoD (Isolated Discipline, OBA - BA). Allen's .332 BABIP is supported by a very good 21% LD rate. Allen's defensive value is likely to be slim. Minor League Splits TotalZone has him as a roughly average defender for his career, although his value has been higher in his most recent stints. Still, sample size on these seasons is too small to make too sweeping of a judgment, and as a first baseman, the -12.5 run positional adjustment means that Allen will have to hit and hit well to be a valuable player at the ML level. If his 12.4% AA walk rate translates to the majors, Allen's raw power could make him an everyday player for at least a few years with Arizona.
Personally, I like the trade for Arizona. With the team going nowhere this year, any loss from Pena's production will be minimal. The trade is by no means a total waste for Chicago, as Pena is team controlled and talented. Still, although Pena will certainly help the White Sox bullpen, there were and still are much more glaring areas of concern. Specifically, either a replacement at 3B so Gordon Beckham (0.3 WAR so far) can continue developing at the minor league level, or a CF to replace the black hole that is Dewayne Wise and Brian Anderson (0.2 WAR so far combined) would've been a much more prudent use of Allen's pull than a reliever.