Presumably sober 19-20 year-old beats up drunk as fuck 17 year-old, whilst throwing the first punch, on a road.
Wow very smart, well played fellas
In future, consider completely leaving the situation - he's drunk. Or, if your friend is really that desperate to be in his first "fight" to tell his bum-buddies about, take it onto the grass - a nasty landing could have led to serious shit.
Sorry if I'm missing some context, but that could have been handled a lot better. A friend of mine was in the drunk guy's position - we were on an island and he lost two of his teeth because of some fuck-wit sober guy trying to act big. I caught the end of it and broke up the fight, carried his ass home with him puking over me on the train, and it wasn't fun. People get feisty when they're drunk, that's a known fact