Rob Gronkowski endured nine surgeries and multiple injuries to nearly every part of his body during his NFL career.

And that includes his head.

In an interview Wednesday night with NBC News’ Philip Mena, the retired New England Patriots tight delved into the impact that nearly two decades of football had on his brain.

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Gronkowski admitted he had “mood swings” that he believes were related to brain injuries suffered on the field and told Mena he’s currently doing brain exercises that include working on a 750-piece puzzle at his home.

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