I know the Pirates have been cited as a recent example of being cautious with young arms in a pennant race, but those were very different situations. 2012, Gerrit Cole. Cole was drafted in 2011 and did not pitch as a pro that year, only 15 innings in the AFL. So yeah, they probably wanted to cap him at around 132 innings across 3 levels in 2012. (And Cole scuffled some at AA that August, and only made one appearance at AAA to finish the season, so he was hardly comfortable yet at the highest level of the minors.) Glasnow is another one they appear to be holding back this season, although he has fewer pro innings than Berrios in the same number of pro seasons, and also had an ankle injury earlier this season (which I guess could mean he's further from his innings limit too, should they decide to call him up soon). And Cole and Glasnow were both more "elite" prospects than Berrios, for what it's worth. It's very hard to find guys comparable to Berrios experience, health, and level who were held back in a pennant race.