Tom Brady's playing days are behind him, but his body didn't get the memo ... 'cause the seven-time Super Bowl champion hit the beach to prove he's still got a rocket arm -- and a shredded physique to go with it!!

TB12 shared a few snaps of his pigskin sesh with his son, Jack, on Tuesday ... days before the NFL postseason kicks off.

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The Fox analyst clearly had that on his mind ... as his caption made note of this special time of year -- which he dominated so often during his 23 seasons with the Patriots and Buccaneers.

"The playoffs roll around and you can’t help but see how the ol' arm feels 😂," Brady said on Instagram.

Brady retired "for good" in February 2023 ... but has made it crystal clear ever since he could still suit up if he wanted.

Just last week, he showed off his retirement bod while golfing with his kid ... as well as several other opportunities to drop the top.

Brady is now a part owner of the Las Vegas Raiders, so folks know he's REALLY done playing ... but -- apparently -- not because he can't.