Castro was fine after getting hit with a Kerry Wood pitch on the inside of the right forearm during live batting practice Monday and isn't expected to miss any time.
But had Castro gone down for a significant amount of time, second baseman Darwin Barney could have been the candidate to get the most time at shortstop.
There are other backup shortstop candidates in camp with some experience at the position such as Adrian Cardenas, Edgar Gonzalez, Matt Tolbert and Alfredo Amezaga. Blake DeWitt also has minimal shortstop experience going back to his days with the Los Angeles Dodgers.
Junior Lake has shown promise but has never played above Double-A. First-round pick Javier Baez is extremely talented but remains a few years away.
So while the Cubs seem to have a lot of options, clearly they don’t have anybody near the talent level of Castro to step in right away in case of an emergency. Who does, really?
Already facing a challenge to become a playoff contender, the Cubs' chances of success would really be in jeopardy if Castro goes down. It's clear that the team's slim chances of winning will require not only good health but everybody performing at or above their career norms.
To Castro's credit, he isn't scared about the possibility of getting hurt, which doesn't mean he is reckless. He said Monday that he's been hit before and he will get hit again.
And when it happens, expect the Cubs' brass to hold its collective breath a little bit longer than usual, just as they were doing Monday when news spread like a wildfire around camp that the talented shortstop took a fastball off the arm.