DeJean, 37, split last season between Double-A Tulsa and Triple-A Colorado Springs and finished a combined 0-3 with a 7.63 ERA between the two clubs. DeJean owns a career record of 30-33 and a 4.30 ERA over 565 career appearances with five Major League teams, including Colorado (1997-2000, 2006), Milwaukee (2001-03), St. Louis (2003), Baltimore (2004) and the New York Mets (2004-05).
Diaz, 25, hit .240 (25-for-104) with nine home runs and 25 RBIs in 37 games with Texas in 2007. He also played in 69 games for Triple-A Oklahoma, where he hit .321 (87-for-271) with 14 home runs and 65 RBIs. In 147 career Major League games with the New York Mets (2004-06) and the Rangers (2007), Diaz has hit .256 with 24 home runs and 73 RBIs.
Hines, 27, spent 2007 with Triple-A Fresno, appearing in 29 games and finishing with a 1-1 record and a 4.69 ERA. In eight career Minor League seasons, including 1999 and 2001-07, Hines owns an 18-22 record and a 4.24 ERA with 41 saves.
House, 28, hit .211 with three home runs and three RBIs in 19 games for Baltimore in 2007. He also played in 110 games at Triple-A Norfolk, where he hit .298 (125-for-419) with 11 home runs and 66 RBIs. In four Major League seasons from 2003-04 and 2006-07, House hit .175 (10-for-57) with three home runs and three RBIs.
House previously played in the Houston organization in 2006, when he hit a combined .352 with 15 home runs and 105 RBIs between Double-A Corpus Christi and Triple-A Round Rock. He also played in four games for the Major League club, finishing 0-for-9.
Niekro, 28, hit .176 (3-for-17) over 11 games for San Francisco in 2007. He also played 47 games at Triple-A Fresno, hitting .301 (43-for-143) with five home runs and 20 RBIs. Niekro has played in 195 career Major League games, all with the Giants (2003, 2005-07), and he owns a career average of .246 with 17 home runs and 79 RBIs.
Niekro is the son of the late former Astros pitcher Joe Niekro, who is the franchise's career leader in victories with 144.
The 24-year-old Manzella hit .264 (119-for-451) in 121 combined games between Class A Salem and Double-A Corpus Christi in 2007. He was named a Carolina League All-Star last season. Originally selected in the third round of the 2005 First-Year Player Draft, the shortstop hit .261 with eight home runs and 100 RBIs in three Minor League seasons in the Houston organization (2005-07).
Muecke, 26, was 9-5 with a 3.90 ERA over 32 games (16 starts) for Double-A Corpus Christi in 2007. Originally selected in the fifth round of the 2003 Draft, Muecke is 31-28 with a 4.29 ERA over 136 career Minor League games (72 starts) over five seasons in the Houston system from 2003-07.