According to Vacchiano, the deal clears $3.475 million in salary-cap room for the Giants. Diehl, 32, is scheduled to become an unrestricted free agent in 2014. It's likely Diehl's 11th season with the Giants also will be his last.
Diehl said last week on NFL Network's "NFL Total Access" that he was willing to redo his contract to help the Giants lock up wide receiver Victor Cruz, who's a restricted free agent. But this move was a separate and long-planned business decision by the Giants, who only were open to bringing back Diehl on their terms.
Follow Dan Hanzus on Twitter @DanHanzus.