Pitchers lose velocity as they put more wear on their arms. Dave Bush went from 89.7 in his rookie year to 89.1, 89.2, two years of 88.7, to 87.9 to 86.5. From 2004 to 2010 he lost 3.2 mph on his fastball. Marcum went from 89.4 in his rookie year to 88.1 to 87.8 to 86.8 to 87.1. He's already losing velocity. Over 2 mph since his rookie year. I don't know how that's not a concern if that trend keeps up.