Johan Santana (shoulder) will open the season on the disabled list. Mets manager Terry Collins made the announcement Thursday when he named Jon Niese as the club's Opening Day starter. It hardly comes as a surprise, as Santana is still in the process of building arm strength and has yet to make his spring debut. The veteran southpaw may still be weeks away from pitching in a game. Jeremy Hefner is the favorite to take his spot in the rotation for now.