The only stat that matters at the end of the season is W's, TEAM W's. Maybe he could win 15-20 games as a starter over a season...if the closer doesn't blow his lead. Or he could potentially save 50 games, making him much more valuable to this team as a closer. Hansen making minor league starts is not to develop him as a starter, it's a move designed to get him the maximum amount of innings to develop his pitches and possibly strengthen his arm. When he's ready for the show, he needs to fill whatever role the team decides maximizes it's chances to win the AL East.