The byline signifies original, on-site reporting. (You don't put bylines on re-fashioned news releases, either.) Putting a byline on what is traditionally regarded as the "gamer," if the reporter wasn't present, is misleading. Even if putting a byline on a gamer that wasn't personally staffed signifies nothing to 99.9 percent of the readers, it's a poor practice, professionally speaking.
If the product of a non-staffed "gamer" is more of what is traditionally called a second-day take or what we'd call a "live feature" -- a feature/profile of someone wrapped inside the report of the athlete's most recent game -- that is different. In that case, byline is appropriate, but no dateline if the site of the game wasn't local.