The best point I've seen made is that Jansen didn't start pitching until like 22 years old. At 17 Chapman was pitching in major Cuban tournaments. Lot more wear on the arm of Chapman, who absolutely has to have that 100+ MPH heater to be an elite reliever. The thing about Chapman's velocity is that it's so ridiculous that he can lose a tick and still be really good. Chapman led pitchers in fastball velocity by 2.4 mph, that's the same as the gap between 2nd and 29th. I know some people will think of Game 7 and get apprehensive, but I don't think that's a fair representation of Chapman because he was missing command as much as velocity. He also has only thrown 840 innings as a pro since he was 17 in Cuba, so while his arm isn't Jansen fresh(500 IP!), I don't think there's much risk of past workload weighing him down. Are there still people pushing for Chapman to be a starter?