Walker isn't a parttime player.. he's just had injuries. Last year, he came back midseason, and played well in the Cards' lineup.
I like your team, but you definitely need some closing help. In H2H, you should atleast have one closer, to get you some W's some weeks, and not completely boot the category. Try to get some potential Closer guys, like Luis Ayala, Mike Gonzalez, etc., some guys that might steal the job, get you some saves. Lose Mesa.