After a career-threatening injury puts back a dream of becoming one of soccer’s elite, a teenage boy must rediscover his form and prove his doubters wrong.

I agree with the interest of the story, and I can see the goal. I think what can make this log line better, is stating the injury. "After being set on fire..."

It seems like a cliche to me. Can you describe what's the newness here. A simple twist will do it, i guess.

You have a clear story, but I feel I'm missing the details.

To paint a mental picture of what we're actually going to be watching for at least 90 minutes, I would add HOW he attempts to do this. What does he need to do to "rediscover his form and prove his doubters wrong?"

I'm sure you have more to the story than just watching him work out throughout the whole film, but that is basicallly all I can read from this logline.