You can't imagine a scenario where a prospect could be rushed? Basically, it's the phenomenon where the lack of the player's skillset results in the development of bad habits and/or the loss of confidence. I think we can see that the entirety of the MLB recognizes this with how few talented players make their debuts at young ages or shortly after being drafted. Clearly the minor leagues serve some purpose. You point to the exceptions, but they prove the general rule: don't rush your prospects. Rooker's age is a red hearing. He's had less than two years of pro-ball. Just because he's older doesn't mean the consequences of him being exposed to the major leagues too soon will be erased. In any case, whether he's rushed or not, he should not be penciled in the lineup when there's an affordable asset like Cruz which can be obtained. Even if we had not signed Cruz, or picked up Cron, I have a hard time imagining a scenario that would have Rooker as an opening day 1b/DH in 2019.