I haven't played around with this system, but judging by the videos it seems they should have vetted their physics system against some priors from real-life such as defender's advantage (attacking is harder than defending) and relative difficulty of actions (defending shouldn't be so much harder than shooting, dribbling and passing). It might also be good to have basic structure for off-the-ball behavior to make it more realistic and organized (e.g. maintain 4-4-2 shape), so that there is always 1 defender behind each opposing player when the team doesn't have possession. That way, it won't look so much like a schoolyard game.