Lets flip this around. Say we were in he same situation but on the winning side and we had Felix on the mound. If a manager trotted out a kid for his first at bat in that situation we would have been laughing our asses off at that manager. Sure at this point in the season there no "easy" way to give Kjerstad his first at bat. But there's a big space between "easy" and what he did last night.
Honestly before he stepped to the plate did anybody think he was actually going to get a hit? The chances of getting a hit there were probably higher for anybody else on the roster (pitchers excluded...lol).