With the news of Brett Favre's retirement today, another possible QB battle at training camp has broken out. The Vikings will either have Tarvaris Jackson or Sage Rosenfels at the quarterback position.
There are many other NFL teams that have possible QB battles at the beginning of training camp, including the Bills and Cardinals.
One of last year's QB battles was between Mark Sanchez and Kellen Clemens of the New York Jets. The job was eventually won by the rookie Sanchez, who helped bring the Jets into the playoffs.
This season also has some QB battles between rookies and veterans. For example, the Rams have said A.J. Feeley is already the starter, though Sam Bradford was the first overall pick.
This is just one of the many possible quarterback competitions in training camp this season.