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The man who stabbed Mark Sanchez -- allegedly in self-defense -- was badly injured himself ... with new photos capturing the extent of the damage.

Max Lewis -- a reporter with FOX59 in Indianapolis -- shared photos of a person he says is the other man rushed to the hospital after the early incident early Saturday morning. Getty

Lewis posted the pictures to Facebook ... and, they are disturbing -- showing a massive, bloody cut on the man's cheek. The neck brace he's wearing is filled with blood .

According to Lewis, the man's family sent him the photo ... but they've asked him not to publicly identify their family members. Play video content

ML did report he's 69 years old ... adding the family says he was "cut in the fight and it went through his cheek and hit his t

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