Nathan adjusted his offseason workouts this winter with the hope adding more agility and flexibility, MLB.com's Jason Beck reports. After struggling in 2014, Nathan is out to prove that he still has something left in the tank. Tigers general manager Dave Dombroski indicated in October that he expects Nathan to begin the season as the team's closer, but a healthy Joakim Soria may be waiting in the wings if the 40-year-old shows any signs of prolonged struggles.