At the same time, in my experience, the players who can have fun WHILE working hard will put more into the game and get more results out than those who see it as just a job. See Hurst's tagline, for example...you have to have commitment, effort, and hard work, but a talented team who has fun is, on the average, going to perform better than an equally talented team who doesn't.
As for TK's statement, I agree...I don't think it's unrelated at all. Again, keeping other factors equal, athletes seem to perform better AND have more enjoyment when they feel a connection with the other athletes they're playing with and the coach they're playing for.