Jeff Ireland was a former kicker himself and he evaluated all kickers with great scrutiny from a perceived "insider" perspective. While Carpenter was good and had been pretty reliable for years, he failed to nail wins in 2 key games the 2012 season and from that moment on Ireland wanted a better kicker. In Caleb Sturgis he saw a young guy with ice in his veins. Make no mistake, Sturgis is good. However, one of the best abilities in the NFL is availability. Caleb still has a power boot and appears to have filled out a bit in the offseason (well his butt looks bigger), but the coach's patience will wane rapidly if the groin strain is serious. The ice is still in his veins but it doesn't count if he's not healthy.
Ireland's lust to draft a better kicker doesn't look all that smart now.