Why did BJ Ryan get released?

I heard that Ryan asked for his release because his velocity was down and the sharpness of his slider was completely gone. Looking up his minor league stats, Ryan pitched 5.2 hitless innings in the minors. He did walk 5 and struck out 4, but he had hitless stuff. I think he asked for his release based on the Cubs acquiring two loogies, John Grabow and Tom Gorzelanny, as opposed to thinking he's done. At least he's thrown a baseball in the past 3 year, unlike one Mark Prior