The Mets removed left-hander Jon Niese from his start against the Rangers on Saturday in the sixth inning because of a rapid heartbeat. Niese was examined by a Rangers doctor to ensure he was not suffering from something serious. Another examination is tentatively scheduled for Tuesday in Detroit. After strange behavior on the mound, Mets manager Terry Collins went out to talk with Niese. "Are you okay?" Collins asked. "My heart's really racing," Niese replied. "I can't get it stopped."