Try this:
<%= form_for @player do |f| %>
<%= f.collection_select :team_id, Team.all, :id, :name, {}, { :multiple => false } %>
<% end %>
This assumes you have an attribute in your Team model called name
. Make sure you add a team reference in the player's model.
If you are using Rails 3, you have to add :team_id
to attr_accessible
, if you are using Rails 4, you have to add :team_id
to strong parameters in the user's controller.