Before Saturday's game in Colorado between the Giants and Rockies, umpires were instructed to keep a close eye on game balls at Coors Field after the Giants expressed concern to the commissioner's office that the Rockies might be using "juiced" balls when batting. Major League Baseball spokesman Pat Courtney confirmed that umps were told to monitor Saturday night's game balls. Courtney said the Giants had spoken to MLB about the Rockies possibly using balls that weren't properly stored in the humidor at Coors Field. "We got the bag and brought it over here about a half an hour before the game," crew chief John Hirschbeck said. "Our clubhouse person brought them out."