I suggest, as does the BMO Harris Bradley Center, that the the only way to ensure complete authenticity of your tickets for one of their concerts, special events, or team games is to purchase them through the main ticket center. So this is a long way of saying be leery of those who are selling ticket.s

I would stay away from scalpers because they tend to mark up the tickets and the games are rarely if ever sold out except maybe for the playoffs.

In recent years, games have seldom been sold out except for the playoffs (this year and several years back). So you shouldn't have to deal with scalpers and like with the Brewers, tickets are very reasonably priced. You can also get great deals online buying during promo periods.