Walter, 24, went a combined 4-5 with a 3.46 ERA in 40 games, including 33 at Quad Cities. He was signed by the Astros as a non-drafted free agent in 2011 out of Yavapai Community College in Arizona.
Brian McTaggart is a reporter for MLB.com and writes an MLBlog, Tag's Lines. Follow @brianmctaggart on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.