It’s nice to add a weapon to your decision-making, but there’s always the question of how you use it.

The signing of Chris Capuano (shown above pitching a two-hit shutout with 13 strikeouts against the Braves last August) has been framed as evidence of the Dodgers placing more faith in sabermetrics, according to this article by Ken Gurnick at MLB.com.

… The Dodgers signed Capuano to a two-year, $10 million free agent deal after newly hired front-office number-cruncher Alex Tamin determined that the lefty fly-ball pitcher was a double fit in the club’s tight payroll and spacious ballpark. …

… Doubters will say his effectiveness tailed off after the second time through the lineup and only 14 of his 31 outings were quality starts. The Dodgers will counter that improvement in his strikeout stats mirror the improvement that led to his finest season of 2005.

His career stats in NL ballparks isn’t pretty: 4-9 with a 12.93 ERA and 11 homers in 86 1/3 innings. Last year it improved to 1-2, 2.89 and one homer in 18 2/3 innings. (Note: I think something went wrong with the stats in this paragraph.)

“My feeling is that the last couple years, you can notice the metrics are a lot like ’05 and ’06 when I had my best years,” Capuano said. “What that told me confirmed what I was feeling, I feel as strong or better as when I was 25. …

The problem I see with this analysis is that you need look no further than Ted Lilly to see its limitations. Lilly, also a lefty fly-ball pitcher, has continued to give up prodigious numbers of home runs in a Dodger uniform – 41 in 269 1/3 innings, even if he did allow none in his final six starts in 2011.

Lilly’s adjusted ERA with Chicago was 122 in 3 1/2 seasons and 115 before he was traded to the Dodgers in mid-2010. With the Dodgers, it has been 98, including 94 last year. Lilly is 36 now, and unlike with Hiroki Kuroda, you can basically say the aging process is showing and that Dodger Stadium isn’t capable of stopping it.

Capuano is 33, which, coincidentally, is the age Lilly was when he unexpectedly had by far the best season of his career in adjusted ERA, 144. But unless you believe that 33 is a magic age, this may not work out well.

Yes, Capuano has been recovering from surgery and struck out 168 in 186 innings for the Mets last year – that does seem significant. But his adjusted ERA was 82, and in his entire career it has never been higher than 113. When he’s not striking out guys, he’s getting hit – hard. And it was only getting worse in 2011: In the second half of the season, he struck out 81 in 83 1/3 innings … with 14 homers allowed and a 5.08 ERA.

And what’s supposed to happen on the road, where Capuano pitches half his games, where he had a 5.42 ERA and allowed 17 homers in 84 2/3 innings? That’s a homer inside of every five innings.

At $10 million guaranteed over two years, do the stats really show that the Dodgers have gotten a good deal?

Sure, Capuano should pitch better in Dodger Stadium than elsewhere – but he needs to pitch better, because – guess what – the guy in the other uniform is going to pitch better, too. And that’s against a Dodger offense that, shall we say, could be challenged.

That’s what I’m afraid the Dodgers haven’t taken into account. Dodger fans will certainly hope for the best, and as a No. 5 starter expectations should be kept in check anyway, but if he’s still deserving of a spot in the starting rotation by July, that might be a surprise.