Madison Bumgarner took another positive step in preparation for his first opening-day start, throwing three scoreless innings Tuesday in the San Francisco Giants' 3-2 victory over the Colorado Rockies.Colorado Rockies starting pitcher Juan Nicasio pitches to a San Francisco Giants batter during the first inning of an exhibition spring training baseball game Tuesday, March 4, 2014, in Scottsdale, Ariz.San Francisco Giants starting pitcher Madison Bumgarner pitches to a Colorado Rockies batter during the first inning of an exhibition spring training baseball game Tuesday, March 4, 2014, in Scottsdale, Ariz.Colorado Rockies catcher Matt McBride reaches for the throw to first base as San Francisco Giants' Juan Perez, right, arrives safely for a single during the fifth inning of an exhibition spring training baseball game Tuesday, March 4, 2014, in Scottsdale, Ariz.San Francisco Giants shortstop Ehire Adrianza, above, watches his throw to first to complete a double play as Colorado Rockies' Paul Janish, below, slides in late to second base during the third inning of an exhibition spring training baseball game Tuesday, March 4, 2014, in Scottsdale, Ariz.