Jose Arredondo began last season in the minors, but quickly joined the Angels' bullpen and went 10-2 with a 1.62 ERA and .190 opponents' batting average in 61 innings while gradually moving past Scot Shields to become Francisco Rodriguez's primary setup man.

Rather than turn to Arredondo as their new closer when Rodriguez departed as a free agent this offseason, the Angels signed Brian Fuentes to take over ninth-inning duties and left Arredondo in a setup role ... where he's posted a 5.55 ERA in 25 appearances.

Arredondo was demoted to Triple-A this morning, with manager Mike Scioscia explaining that he "needs to work some things out" and "has obviously taken a small step backwards." There's no getting around the fact that Arredondo has allowed far more hits and runs than last year, but delving a little deeper into his performance reveals some interesting things.

While certainly very good, his 57/22 K/BB ratio in 61 innings last season wouldn't normally produce a 1.62 ERA or .190 opponents' batting average. Arredondo was extremely fortunate in terms of his balls in play being converted into outs, which the Angels' defense accomplished an astounding 76 percent of the time compared to the AL average of 69 percent.

The opposite has been true this year, as his 27/12 K/BB ratio in 24 innings is much better than his 5.55 ERA--and not far from his 2008 rates--but the Angels' defense has turned his balls in play into outs just 60 percent of the time. Scioscia is no doubt right that he could stand to work on some things and his increased line-drive rate has also played a part in the ball-in-play numbers, but the biggest difference between last year's 1.62 ERA and this year's 5.55 ERA basically boils down to luck.

Last season Arredondo struck out 23 percent of the batters he faced, walked 9 percent of the batters he faced, induced 51 percent ground balls, and served up two homers in 244 plate appearances. This season Arredondo has struck out 25 percent of his batters faced, walked 9 percent of his batters faced, induced 49 percent ground balls, and served up zero homers in 110 plate appearances.

The nuts and bolts of his performance really haven't changed much at all, and in fact in some ways have actually improved. As usual focusing on ERA fails to tell the whole story, particularly for relief pitchers, and a deeper look at Arredondo's numbers suggests that he would have turned things around soon enough. However, the guy with a 1.62 ERA from last season likely isn't coming back because he never really existed outside of a world where the defense behind him is played by four Ozzie Smiths and three Willie Mayses.

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