Major League Baseball plunged into its first work stoppage in a quarter-century when the sport's collective bargaining agreement expired and owners immediately locked out players in a move that threatens spring training and opening day. The strategy is management's equivalent of a strike under federal labor law. The move ended the sport's labor peace after 9,740 days over 26 1/2 years. Teams decided to force the long-anticipated confrontation during an offseason rather than risk players walking out during the summer, as they did in 1994. Players and owners had successfully reached four consecutive agreements without a work stoppage.