Borkowski and Castillo have the right to refuse the outright assignment and become free agents, while Cassel and Houston automatically become minor league free agents based on each pitcher’s respective minor league service time.

Borkowski, 31, was 0-2 with a 7.50 ERA (30ER/36IP) in 26 appearances for the Astros in 2008.  In 181 career Major League games (21 starts) with Detroit (1999-2001), Baltimore (2004) and Houston (2006-08), he is 13-20 lifetime with one save and a 5.87 ERA (226ER/346.1IP).

Cassel, 28, was 1-1 with a 5.64 ERA (19ER/30.1IP) in nine games (3 starts) for the Astros in 2008.  In 15 career big league games, including seven starts, over two seasons with San Diego (2007) and Houston (2008), Cassel is 2-2 with a 4.92 ERA (29ER/53IP).

Castillo, 27, hit .281 (9x32) with two RBI in 15 games for the Astros in 2008.  In 127 combined games between Houston and San Francisco, he hit .246 (105x426) with six home runs and 37 RBI.  He was claimed off waivers from the Giants by the Astros on August 20.  In 592 career Major League games over five seasons with Pittsburgh (2004-07), San Francisco (2008) and Houston (2008), Castillo has hit .254 (487x1918) with 39 home runs and 218 RBI.

Houston, 29, was 1-3 with one save and a 7.54 ERA (38ER/45.1IP) in 39 games for Triple A Round Rock in 2008.  He was claimed by Houston off waivers from Toronto on Dec. 12, 2007.