Sierra is a 23 year old reliever that has been around since 1999...was only in A ball last season. Does not look like anything special.
MINOR LEAGUE PITCHING STATS
Year Team W L ERA G GS CG SHO SV INN H R ER HR HBP BB SO
1999 R-OAKLND EAST 1 3 5.02 6 5 0 0 0 28.2 32 24 16 1 1 19 27
1999 R-OAKLND WEST 2 4 4.11 14 6 0 0 1 57.0 58 42 26 2 3 32 54
1999 R-OAKLND WEST 1 1 3.18 8 1 0 0 1 28.1 26 18 10 1 2 13 27
2000 R-OAKLAND E 1 2 3.57 4 4 0 0 0 22.2 21 9 9 0 1 9 19
2000 R-OAKLAND W 4 2 2.22 10 9 1 0 0 65.0 56 27 16 1 4 24 50
2001 R-ATHLETICS 2 1 3.02 12 6 0 0 1 44.2 45 19 15 1 3 9 41
2002 A-VANCOUVER 0 2 6.11 9 7 0 0 0 28.0 42 24 19 0 3 17 23
2002 R-ATHLETICS 2 1 4.64 6 6 0 0 0 33.0 29 19 17 2 7 10 35
2003 A-KANE COUNTY 3 5 2.09 51 0 0 0 17 60.1 46 23 14 2 8 24 52
2004 A-TAMPA 2 3 3.33 45 0 0 0 28 48.2 44 22 18 2 2 45 57
Currently with the Trenton Thunder:
http://www.minorleaguebaseball.com/app/ ... pid=430682