As part of the NFL's International practice squad program, the Cardinals were assigned Mexican national Eduardo Castaneda, a 25 year old linebacker. Castaneda played a season in the former-NFL Europe and spent last year on the Houston Texans practice squad. The program allows for a team to select several players that they are interested in and then the league assigns each team a player. That player receives a 'practice squad exemption' so that the team can carry 9 players on the practice squad instead of just 8. There are some other 'quirky' rules with the program including, the player can play in preseason games but can't be added to any teams active roster. So basically he's guaranteed to be on the squad all year (there's no reason to cut him unless he gets in trouble) but he's also guaranteed not to crack any NFL roster in 2008. The team will have the option of signing him to a contract after the season, but until then he's just another warm body in practice.
It sounds like the Cardinals were interested in Castaneda not only because of his Mexican heritage (they're trying to boost their popularity with our neighbors to the south) but also because he is a past teammate of former Cardinals' lineman and current Cardinals' manager of international business ventures, Rolando Cantu. Castaneda (6'3 253) appeared in the season finale with the Colts in 2005, but didn't register any stats. During his season in NFL Europe with the Rhein Fire, he registered 10 tackles.