Zack Greinke pitched in the majors for 5 years and had a pedestrian 4.28 career ERA to show for it, but he had a lot of potential. He won the Cy Young the following year. I'm not comparing Greinke to Garza, but to say a pitcher can't change after 5 years of not showing signs of improvement is a little silly. FWIW, Cliff Lee had a 4.64 ERA over his first 6 years before he won the Cy Young at the age of 29. His ERA the year before was 6.29 over 97IP. IIRC, all he did was develop a cutter into his repertoire and it changed everything for him. It can be as simple as developing a new pitch, a change of scenery, or having something just click. There's nothing to suggest Garza is destined to remain the pitcher he's been this far into his career. Anything can happen