"Significant improvement" is just about the worst possible way to phrase Smith's progress from the injury because it suggests the recovery is a gradual process where you could expect some improvement from day-to-day, week-to-week, or month-to-month.
But that nerve is going to be like a light switch: It's either on or off, there is no in between.
Waiting for the light in a dark room to "significantly improve" without flipping the switch is a fool's errand.
With all due respect, you just contradicted yourself.
If the injury isn't a "gradual process" but a light switch, then if the switch doesn't/hasn't turn/ed on the light, then there's no "significant improvement."
However, if the injury involves a gradual recovery, then two inches of growth in the nerve is not significant improvement when you measure what it will take for the nerve to grow to where it should. But it would be minor improvement and an indication of showing progress.
I'm no doctor, but from what I've read, the nerve has to "grow" back. If so, we shouldn't be looking at "significant improvement." I'd be more interested in "gradual improvement," and that would mean telling me how much the nerve has grown in two months.
I don't expect him to be able to run like he did before the injury - at least not now. But I'd like to know the nerve is making progress even if he's not back to being 100 percent.