INDIANAPOLIS (AP) -- Colts general manager Ryan Grigson was unusually busy on the opening day of offseason workouts.
Costa's surprising decision came just five weeks after he left Dallas in free agency to presumably compete for Indy's starting job and could be a major blow for Grigson's plan to reinforce an offensive line that has struggled to create running lanes or keep Andrew Luck from taking too many hits.
''Phil feels it's in his best interest to retire from the game,'' Grigson said in a statement released by the team. ''We certainly understand and wish him nothing but the best.''
Costa's listed agent, George Mavrikes, did not immediately respond to a message left by The Associated Press.
Indy's players and coaches are not scheduled to be take questions until Wednesday.
The Colts, who have only five picks in next month's draft, don't have a lot of options left to fill holes.
They released two-year starter Samson Satele in a cost-cutting move in early March, then opted to sign Costa to a contract rather than trying to outbid the Browns for center Alex Mack. That leaves second-year center Khaled Holmes as the current favorite to be the opening day starter.
Holmes snapped for Matt Barkley in high school and at Southern California and was a fourth-round pick in last year's draft, but was injured early in training camp. But he played in just three games, making no starts.
The retirement of the 26-year-old Costa, who made 20 starts in four seasons with Dallas, opened up a roster spot and Grigson wasted no time in filling it.
Later in the day, Grigson added Anderson, a 5-foot-10, 194-pound safety who made six starts and played in 48 games over four seasons with Philadelphia.
Anderson has 47 career tackles, four passes defensed, one interception and two forced fumbles. He also has 46 career special teams tackles.
Gordy, who had nine tackles and one interception in 12 games last season, also signed his qualifying offer from the team.
He was acquired in a trade with St. Louis in August 2012.
In three NFL seasons, Gordy has 77 tackles, four interceptions, one sack and one fumble recovery.
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