Escalona, who was acquired from Philadelphia on Jan. 10 in exchange for Minor League infielder Albert Cartwright, spent the 2010 season as a reliever at Double-A Reading, going 4-8 with a 3.81 ERA and 10 saves in 50 appearances.
Escalona, 26, has some Major League experience, making 14 relief appearances for the Phillies in 2009. He earned his first Major League win in his first game, hurling a scoreless inning on May 17, 2009, at Washington.
Leon spent most of the 2010 season at Class A Lexington, where he was 2-2 in 26 relief appearances with a 2.33 ERA, four saves, 23 walks and 60 strikeouts. He also made 18 relief appearances at Double-A Corpus Christi, where he was 0-2 with a 7.83 ERA.
The 24-year-old Leon, a native of Venezuela, was originally signed by Houston as a non-drafted free agent on Feb. 7, 2005. He also pitched for Aguilas in the Venezuelan Winter League this offseason.
Villar, 23, made his Major League debut in 2010 as a September callup, posting a 0-0 record in eight relief appearances for the Astros with a 4.50 ERA, three walks and three strikeouts. Prior to his callup, he was 4-7 in 36 appearances (11 starts) at Double-A Corpus Christi with a 4.15 ERA, five saves, 42 walks and 68 strikeouts.
Villar was the Hooks' Pitcher of the Month for April after posting an 0.71 ERA in seven appearances with a save. He has a 3.26 ERA in 118 career Minor League appearances (47 starts). Villar, a Dominican Republic native, was originally signed by Houston as a non-drafted free agent in July 2005.
Brian McTaggart is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.