It doesn't take a Rhodes Scholar to know some of the most commonly misrepresented memorabilia involves baseball's biggest stars. Albert Pujols is a prime example, and both his foundation and those who study the Cardinals are offering a primer on the slugger's habits when it comes to equipment and jerseys.
You want to believe it's real. The seller wants you to believe it too. Maybe it is. Sometimes even authenticators don't know for sure. You can lower the odds in your favor by knowing a little about the player.
In the case of Albert Pujols, the problem of fakes has become so widespread, they've devoted an entire page of the Pujols Foundation website to the issue.