I'd abstract almost all of it.
What's important to you as a DM? Do you want a result that makes sense, or one that is narratively satisfying? Will the PC's be actually playing in a game of Hockey & Hosers?
If simulation is more your style, have the opposing teams make Athletics checks in each "quarter," with the winner scoring on the loser, and maybe scoring, say, one point more if they beat them by 10 or better. Let the PC's make Athletics checks to sway the score one way or the other (maybe each PC can try and either make a goal on their own, or they can block another's attempt, in each quarter).
If you lean more on the narrative side, it should, of course, come down to a dead heat with the PC's against the other side. In this case, you might want to run it like a Skill Challenge in the final round, with each success getting closer to the final goal, until, with the final success, they score the winning goal and win it all.
If the PC's aren't participating, just determine the winner randomly.
It might be interesting to make it a bit more combat-focused. In this case, HP is essentially the clock, running out gradually until it reaches 0. If the PC's can "attack" the goal enough (give it some Defenses), each "hit" might score a point. To defend their own goal, they need to heal and provoke.
I'd go with a skill challenge kind of thing.
The Cleric-type might be able to challenge a goal the enemies make on a technicality ("That was clearly a foul!")
The Rogue-type might be able to anticipate how they'll score next ("Look, I heard the locker-room chat, they're going to try the Poison Dragon play.")
The Fighter-type might be good at picking fights with the others, distracting them from their end result ("I'm going to punch the big guy. I might get some bench time, but I'll neutralize the worst of it.")
The Wizard-type might have some tricks for getting goals ("I'll teleport it right in front of you, don't worry.")
Anyway, brainstorming, throwing ideas against the wall. Let us know how it turns out, sounds cool!
