The Aggies finished the 2011 season outside of the Top 25 after they turned in a disappointing 7-6 record. Preseason polls are mainly determined by what a team did the previous year so the Ags' current position in the AP poll is not surprising.
The preseason ranking is inconsequential at this point. If you are not in a BCS conference, then being ranked outside of the Top 25 is a major detriment towards getting into a BCS game. Because of A&M's membership in the Southeastern Conference, this is not an issue.
The Aggies can still achieve all of their goals by winning the games on their schedule in 2012. This is not a case where they will need any help. A&M's membership in the SEC West ensures that a good season will be rewarded with a good bowl.
A&M has as much talent as any team in the country with multiple players on award watch lists. Luke Joeckel, Jake Matthews, Patrick Lewis, Ryan Swope, Christine Michael, Damontre Moore and Sean Porter are all being considered for individual awards.
The major issue facing the Aggies is their lack of depth. Their starters can match up with any team in the country but at a lot of positions, the backups are a question mark.
This is particularly true on the interior defensive line where the Aggies have no proven backup defensive tackles. In the SEC where you can almost guarantee some of your starters are going to miss games, this is a major concern.

If the Aggies win all of the non-conference games and go 4-4 in the SEC to finish with an 8-4 season then they will likely end the year in the Top 25. The final polls in 2008, 2009 and 2010 featured an SEC team in the top 25 that finished the regular season 8-4 and won its bowl game.

The Aggies are unranked because they underachieved in 2011 and lost record-setting players in Ryan Tannehill and Jeff Fuller from that squad. It was recently announced that redshirt freshman Johnny Manziel would take over at quarterback for the Aggies.
A&M is entering a new conference with a new head coach and new systems on offense and defense. It is understandable how many in the media are taking a wait and see approach with this team.
Luckily for A&M, it is in a position where if it takes care of business on the field the rankings will take care of themselves.