The Giants said their defensive captain underwent the test in New York and was examined by team physician Dr. Russell Warren and Dr. Frank Camissa, chief of the spinal surgical services at the Hospital for Special Surgery.
The 31-year-old Pierce originally sustained a burner when the Giants played Arizona on Oct. 25. He had very little discomfort until practice this week, when the club's medical staff scheduled the MRI exam.
"I'm shocked with what I heard from the doctors this afternoon," Pierce said in a statement released by the Giants. "I had no idea that what happened a few weeks ago could keep me off the field. I didn't think it was that serious.
"I'm going to do everything the doctors tell me to do so I can get back out on the field as soon as possible."
The Giants (5-4) will host Atlanta on Sunday. New York, coming off its bye week, has lost four straight games.
Pierce, in his ninth NFL year and fifth with the Giants, has 55 tackles one sack, and one forced fumble in nine games this season. He was looking forward to trying to help New York snap its losing streak on Sunday against the Falcons (5-4).
"This game means a lot to us," Pierce said earlier Friday. "For one, we need a win to get out of this four-game slump and, two, it will help us in the playoff hunt. We are tied for one of the wild card spots and you always want to win the head-to-head battles."
Pierce played in 15 games last season after appearing in all 16 contests each of the previous two seasons. He has led the Giants in tackles for the last three seasons and missed only four regular-season games since leaving the Washington Redskins to join the Giants.
He spent much of the past year in the spotlight after helping former teammate Plaxico Burress when the wide receiver accidentally shot himself in the thigh in a New York nightclub.
Pierce drove Burress to the hospital and then took the gun that Burress used back to his home in New Jersey, later arranging to get it back to the wounded receiver's home. Pierce testified before a grand jury, which declined to indict him for his role in the incident.