If you've ever watched a game, and I can't be sure you have, there is inevitably a guy who went 0-4 with 3 bullets right at someone and another guy who went 1-3 with two horrible looking strkeouts and a bloop single. We know who really hit the ball into bad luck and who had a **** day.
Same applies to a pitcher. Maybe he gave up 5 runs in 6 innings but pitched pretty well. That fat guy in the uniform, the one that knows more baseball than we'll ever know, was watching the game and decided to leave him on the mound simply because he wasn't getting hit hard. And he gets the win when his line reads 6 IP, 5 ER, 9 H, 2 W, 5 K. The win should tell you something even if you can't see it in the stat line.
Of course, you have to accept that the fat guy in the uniform actually knows baseball better than you and I'm not sure you can accept such a thing.