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NEW YORK –Two-time Superbowl champion Leonard Marshall made a living destroying quarterbacks as a member of the NY Giants from 1983 To 1992.

The defensive lineman is also known for delivering this hit on San Francisco quarterback Joe Montana in the NFC Title Game 1991. It ended Montana’s career with the 49ers. These hits took their toll, not only on opponents but also on Marshall, who says he does not know how many concussions he suffered in his career.

The effects of those concussions started to cause problems in his daily life, beginning in 2007. Marshall, along with hall of Famers Tony Dorset and Joe DeLamielleure have been diagnosed with chronic traumatic encephalopathy, or CTE.

CTE is a degenerative condition many scientists say is caused by head trauma and linked to depression, dementia and even suicide … which was the cause of death by his longtime friends Dave Duerson and Junior Seau.

Former Jets receiver two-time Pro Bowler Wesley Walker also admits to having memory loss as well as narrowing of his spinal chord resulting from the hits he sustained over a 12 year career from 1977 to 1989. Both he and Marshall agree the NFL knew about the effects of concussions.

The film Concussion stars actor Will Smith as the forensic neuropathologist Dr. Bennet Omalu. He discovered CTE in the brain of former Pittsburgh Steelers center Mike Webster in 2002.

Marshall worked on the film as a consultant and attended the premiere. Despite his health concerns, Marshall runs a successful business, “the Soup Man” along with CEO Jamielson Karson and Larry Thomas, better known as “The Soup Nazi” on Seinfield.

At 54 years old, Marshall realizes he’s in uncharted territory. And with a family of three kids and a wife, he is brutally honest — the future scares him.