AZ defensive coordinator Vance Joseph sprung the clip on Watt during a team meeting just before the NFL legend's final game against San Francisco ... and almost immediately after it began playing, Watt openly sobbed into his hands.

The video consisted of a grip of messages from Watt's family, friends and former NFL rivals -- and J.J., who announced on Dec. 27 he'd be done with football after this season, could hardly keep his eyes open for it.

The montage started with J.J.'s brother, T.J. Watt, saying, "Brother, J.J., I just want to say congratulations on retirement."

"You ending up in the NFL and you being Defensive Player of the Year, and you having all the success that you had, showed me that it's possible."

Aaron Rodgers, Peyton Manning, Dak Prescott and Tom Brady also congratulated J.J. on everything he's accomplished in the NFL ... and the impact he's had on their careers.

"Man, you were a pain in my ass for a long time," Brady said. "It was an honor to share the field with you."

J.J.'s other brother, Derek Watt, also shared how thankful he was to witness J.J.'s career.

J.J.'s parents, John and Connie, and his wife, Kealia Watt (who was holding the couple's newborn son Koa), appeared on-screen too ... with all expressing their gratitude toward the 33-year-old defensive end.

"It has been such an honor to watch you work your ass off these past years and do whatever you needed to do to be the best," Kealia said. "You’ve been so generous and kind and loving to everybody around you, and you never forgot who you are."

"I know Koa will be so proud to be your son."

J.J. -- a three-time Defensive Player of the Year -- wrapped his career on Sunday against the Niners with two sacks, three total tackles and a pass breakup.

Up next for the star? Canton, Ohio in five years.