"unforced error" and "forced error" already are sports jargon (baseball) and from context "unforced error" must have been intended, which is similar to "own goal" but doesn't imply points being scored. (It's not possible for the defending team to score against itself in baseball anyway, so "own goal" would never really be applicable... though actually the pitcher can walk a run in, I guess that's like an own goal!)

Baseball doesn't distinguish between forced and unforced errors: a ball put in play that results in a baserunner is either a hit or an error. The forced/unforced distinction comes from tennis as far as I know.

I thought they were using tennis analogy, where player hitting the ball out or on the net without being forced to by the opponent counts as an unforced error.

Baseball just has "errors." Tennis has "unforced errors." American football has fumbles, interceptions, safeties, and lots of ways to draw a penalty. I'm probably leaving out other bad things you can do, too (hiking it over the punter's head, or stepping out of bounds, for instance).

I think if we're using it in a non-sports context, "own goal" and "unforced error" are both appropriate.