London Open Polo Tournament 21/22 August

You're better off working out team plays than individual roles, for instance:

Defensive:
Both players tracking back with their players "man on man", no risky challenges.
One player on the hussle, one on the other player/pass.
Both players on the hussle, risky, good for when there's little time, etc.
One player on the hussle, one ready to break for a pass whilst blocking the opposition's passing line.
One player on the hussle, one in the D, good for when you have a goal lead but boring to watch.

Offensive:
Three out on possession, one player always covering breaks/long passes.
Lots of blocking/intervention to allow your teammate through with possession.
Hold midcourt in small circles to draw in players then make fast breaks/passes to goal.
Larger circles, allowing the passing line to keep moving between your players... pass and break when the opportunity arises.
Long passes up court to an aggressively positioned player, risky.
Breaks to goal with a player following for the pass if the break fails, or for goalie deflections (means you always have someone to cover breaks).

Polo is so fast with few players that it is difficult to always have a "striker", etc. It's possible, but I don't see it as a winning strategy anymore, flexible teams are more unpredictable, with no individual roles and more diversity in their plays.