Martinez, a team captain and the defensive signal-caller, will miss the remainder of the season. It's a crushing blow to a Giants defense that surrendered a game-winning drive in the final seconds on Sunday for the second consecutive week.
The noncontact injury for Martinez occurred when he raced to the sideline to make a tackle on the opening drive. He fell to the ground awkwardly before reaching Atlanta's Cordarrelle Patterson.
Martinez, 27, lay facedown until he eventually was helped to his feet, and he needed assistance from the trainer as he limped off the field. He immediately hobbled into the locker room in obvious pain and was ruled out of the game rather quickly.
The Giants (0-3) were hoping for better news on one of their top defensive players. Martinez was an integral piece on a strong defense last season.
"Hopefully it's not serious," coach Joe Judge said after the loss. "Blake is obviously a key part of our team; he's a leader, he's a hard worker, he's a tough dude."
Martinez led the Giants with 21 tackles entering Sunday's game. This after leading the team with 151 tackles last season, his first in New York.
It was his fourth straight season with at least 130 tackles. But that streak will come to an end because of the Week 3 injury.
Martinez signed a three-year, $30.75 million deal with the Giants last year.