Gomes or Heisey in LF?

At 39-33, the Cincinnati Reds currently sit one game back of the St. Louis Cardinals for the division lead in the National League Central. Cincy’s starting pitchers (12th in the NL in xFIP) and ‘pen arms (11th) haven’t really stood out, and the defense has been middle-of-the-pack (eighth in UZR). The offense is the only unit to rate in the top half of the Senior Circuit, as Reds hitters rank second in Park-Adjusted Batting Runs.

Jonny Gomes is doing his part at the plate, slugging .285/.342/.491 with a .352 wOBA in 243 plate appearances. The erstwhile Ray has contributed +4.3 runs with the bat so far, drawing the vast majority of starts in left field for the Reds. During the interleague portion of Cincinnati’s schedule, Gomes has mostly DH’d. Unfortunately, that’s not an option the rest of the year. Once you consider Gomes’ lumbering defense, the Reds might be costing themselves runs by playing him over rookie Chris Heisey.

During his big league career, the 6-1, 225 pound Gomes has a -24.7 UZR/150 in left field and a -16.2 UZR/150 in right field. Pro-rated to 150 defensive games, Total Zone has him at -15.9 runs in left and -24.3 runs in right. Few players in the game punt as much value with the leather — despite Gomes’ quality hitting, he has contributed just 0.1 Wins Above Replacement this season.

Heisey, meanwhile, is considered a much more well-rounded prospect. A 17th-round pick out of Division III Messiah (Pa.), Heisey hit a combined .296/.367/.459 in the minors while rating very well in center and the outfield corners per Total Zone. Prior to 2010, Baseball America called the 25-year-old a “plus defender in the outfield corners.” Heisey projects as an above-average defender in a corner spot, and he reminds me of a David DeJesus-type.

So, how do the two match up? Let’s take a look at Gomes’ and Heisey’s rest-of-season CHONE projections. Offensively, Gomes projects as about +.014 runs above average per plate appearance. Heisey has just 56 plate appearances at the MLB level, with a .413 wOBA. His rest-of-season CHONE forecasts him as -.012 runs below average per plate appearance. If each receives, say, 300 PA from here on out, Gomes would add a little more than four runs above average with the bat while Heisey would be about four runs below average.

Offensively, advantage Gomes. But it’s extremely difficult to envision a scenario in which Heisey doesn’t make up that eight run difference in offensive value with the leather. CHONE thinks that Heisey would actually rate as an above-average center fielder. Let’s say that Heisey rates as a +10 run defender in left per 150 games and Gomes a negative 15 (which is probably generous). If each plays something like 80 more defensive games this season, Heisey would add roughly five runs in value, while Gomes would surrender about eight runs.

Admittedly, the numbers I use are presented as a speculative exercise, but the Reds could be punting a half-win in value for the rest of 2010, perhaps more, by preferring Gomes over Heisey. The NL Central race is close at the moment, but CoolStandings gives the Reds a mild 32% chance of clinching a playoff berth. They’ll need to optimize the talent on hand to stay in the race, and it doesn’t appear as though the team is doing that in left field.