I don’t know but Kirk sure looked fatigued the last third of last season and his numbers took a corresponding down turn. It could have been a case of correlation does not imply causation but I highly doubt it. He is out of shape for a pro baseball player playing a physically demanding position. His cardio is likely slightly above par of an average middle aged man. If Jansen has another injury keeping him out a number of weeks, Kirk can’t be counted on to take on the extra workload.