Who knows what Beane is really planning with my A's now.
If your looking for a reliever that has posted great numbers since haveing been called up then maybe Kiko Calero, not really young at all as he will turn 30 shortly before the season. Two seasons of limited middle relief with St. Louis and he accumilated a total of 83.2INN, 98K's, 30BBI, 56HA, 2.812ERA, 1.034WHIP. Thats a nice K rate of 10.6 per inning.
As bad a weakness as middle relief was last year I think he was aquired only with the intention of useing as a reliever. Juan Cruz seems more likely to get the call to the rotation should D. Haren, D. Meyer, or J. Blanton falter in the rotation. J. Cruz is a nice sleeper but I dont see him as a J. Santana comparison type.
EDIT: 10.6 per 9 innings.

"Son we would like to keep you around here but were trying to win a pennant this year."