Carlson announced his retirement Tuesday, ESPN's Adam Schefter reports. The 30-year-old Carlson has a history of concussions, and he never lived up to the promise of his first two seasons. He averaged a 53-600-6 receiving line with the Seahawks in his first two years, but he has since failed to top 350 receiving yards in any one season. With the former second-round draft pick out of the picture, Arizona's shaky depth chart at tight end looks all the more questionable. 2014 second-round selection Troy Niklas is the favorite to start, despite catching just three passes in seven games as a rookie. While athletic for his size (6-6, 270 pounds), Niklas doesn't profile as a high-volume receiver in the NFL. That isn't necessarily an issue, as the Cardinals have plenty of capable pass-catchers at wide receiver and running back. For tight ends, the team also has former basketball player Darren Fells, along with 2015 seventh-round selection Gerald Christian. Expect Niklas and Fells to compete for the starting job.