Tony Gwynn Jr. recently signed a one year contract with the Los Angeles Dodgers for just under $700k.

The deal is being labeled as a steal for LA by smart folks around the blogosphere. While I agree that, in this market, it’s definitely a nice pick-up to add Gwynn Jr. for under a million bucks, I’m not sure it’s that great of a deal.

Gwynn Jr. had a decent offensive year in 2009, posting a .311 wOBA. However, last season in 339 PAs he was dreadful, hitting .204/.304/.287 (.276 wOBA). However, in those two seasons, he posted WAR values, courtesy of FanGraphs, of 2.4 and 1.7 respectively.

That value is largely due to his centerfield defense, which according to UZR says that he was 18 runs above average in 207 games in center, and 23 runs above average in 218 total games in the outfield with the Padres.

We know that he *probably* wasn’t really that good, due simply to regression to the mean – the fact that, if he played another 218 games under the same conditions, he would likely rate closer to average.

But that is true with all extreme fielding performance. The question I’m more interested in is if Gwynn Jr. is even close to that good defensively. There’s a well known theory (or fact) that it’s harder to hit in Petco because of the size and layout of the park and the heavy marine air. Well, if that is true for hitters, wouldn’t the opposite be true for fielders? The heavy air will, in theory, hold would-be doubles or home runs in the air just long enough to make somewhat routine catches look like great ones.

While some defensive metrics (like UZR) have build-in park adjustments, I’m just not sure how much I trust the numbers, given all the speculation about potential biases in the data that may impact the final calculations – before we even consider the park effects.

While it may look like I’m ripping Gwynn’s defense *after* he leaves for the Dodgers, as I’ve touted his fielding ability numerous times here in the past, it’s more a realization that picking up players solely (or mostly) because of their impressive fielding stats can be a dangerous move, much more so than picking up a solid hitter with suspect fielding numbers.

In the end, it’s still a good move for the Dodgers, as $700K isn’t going to kill them, even if Gwynn Jr. – worst case – becomes a defensive liability in center. More than likely, he’s a little above average in the field, quite a bit below with the bat, and he’ll be a solid enough pick-up for LA.

For the Padres, losing Gwynn Jr. could have stung a bit if they were planning to compete in 2011, but with the current state of transition, losing a fringe guy like Gwynn Jr. just isn’t that significant.*

*That’s without considering the fact that you have to see “Gwynn” on the back of a Dodgers jersey again.