The pitcher's age has a lot to do with it also. At under 25, men are still growing and strengthening naturally. During this time the risk of injury is a little higher due to tendons still maturing. Years ago, young pitchers were rarely called up before they hit 25 as they were gradually building their innings in the minors. When they eventually got called up, they were good to go for the full season and were usually the team's fourth or fifth starter, which helped negate some of the innings.
Sanchez just turned 24, so he's kind of on the cusp. I think his off season regiment advanced him enough where i think he could handle staying in the rotation, mainly because his delivery isn't that violent and doesn't throw a high percentage of curve balls.