I worked with the Notre Dame baseball team the past 2 years and got to see Hansen quite a bit. This past year he was amazing. He pitched in all 3 games that we played them and not only did he save the games, he manhandled our team (and ND is a good hitting team). He has an amazing fastball that few hitters can catch up to. His slider is one of the nastiest pitches I've ever seen. Since his fastball is so effective, hitters have a hard time picking up his sliderl and locating it even when it crosses the plate.
Last year he was good, but lacked a quality changeup, which he added last summer in the Cape Cod league. His changeup literally made ND batters look foolish. Our best hitters batting .350 were striking out easily on 3 pitches.
Through talks with the players and coaches, I have heard he was solely chosen by the Red Sox to be used as a closer, potentially this year in the post season. He wasn't the highest rated pitcher or reliever, but was rated #1 in ability to make it to the majors first. He will not be used as a starter because he does not have another pitch and he's never started in college and lacks the starter mentality. He pitched a 2nd inning against ND and after 5 batters, we started to break him down and he looked shaken.
