The Astros finished 19-7 in June and surged to the top of the American League West heading into a three-game series at Colorado. Colton Gordon will be on the mound for Houston while the Rockies will counter with Chase Dollander in a matchup of rookies on Tuesday night in Denver. Gordon made his major league debut against Kansas City on May 14 and got his first big-league win in his fifth start, against Cleveland on June 6.