New England linebacker Ted Johnson announced his retirement Thursday after a 10-year NFL career, saying he decided to retire rather than risk further injury following a series of concussions. A member of three Super Bowl champion teams in New England, Johnson notified the team of his decision a day before veterans were scheduled to begin training camp. His retirement further weakens the inside linebacker position. Tedy Bruschi, the other starter there, has said he will sit out this season after suffering a minor stroke last winter. Johnson, 32, was drafted by the Patriots in the second round of the 1995 NFL draft out of Colorado, the 57th overall player selected. The 6-foot-4, 253-pound linebacker started 106 of 125 regular season games and was credited with 865 career tackles and 11? sacks.