The Cubs have had an uncanny run of good health in the starting rotation the last few seasons. The most severe injury involving a starter the last three years was Jake Arrieta’s month-long absence due to a hamstring strain late in 2017. Whether they ever add another starter or not, it might be helpful to look at their overall rotation depth.
After all, counting on a continuation of their nearly impeccable injury record is a risky proposition. Like riding a heater at the blackjack table, you’re bound to bust eventually. And even if their core five arms all remain healthy, there will be times — long stretches without off-days or emergency double-headers — when a spot-starter is needed.