I'm an internationally competitive marathon runner, and I know from personal experience that more likely than not, people rebound from stress fractures pretty easily. This said, stress fractures require you to take off at least 6 weeks from training, meaning that, the athlete needs to regain stamina over the course of a few months before being up to 100%...
... and if you're under the assumption that skating full-speed for 4 minutes while landing crazy jumps doesn't take stamina, that's a whole other issue that you need to wrap your mind around. This, with the fact that it takes time to become comfortable enough with a program to really sell it, makes it likely that Mirai won't be at 100% at this first event (though I doubt that many skaters are at this point).
So, in short: yes it has an effect, but no, we shouldn't panic.
Ladies (I'm most familiar with them)
I wish Mirai does well, and I'd normally put her in the top 3, but I'm concerned about what we heard about her fairly recent injury.
3. I guess Contesti