J.J. Watt took a hard shot at Austin Rivers on social media.
Because of a fascinating NFL versus NBA debate.
Some NBA players believe they're the greatest athletes on the planet and could easily cross over into the NFL, thanks to the speed, power and overall athleticism required to excel on the court.
Some NFL players are adamant that American football is the best sport in the world, and NFL stars could make it in the NBA if they simply played another sport.
"I can take 30 players right now in the NBA and throw them in the NFL," Rivers said. "You cannot take 30 NFL players and put them in the NBA."
Watt strongly disagreed and quickly called out Rivers, who played for seven NBA teams in 11 seasons.
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"You don't got a job in either right now. Go head and try it," tweeted the former NFL star and current Burnley co-owner.
Watt added: "For the record, I could absolutely not play in the NBA. 6 hard fouls is about all I could give you and call it a day."
One fan mentioned that Watt would basically be "Draymond Green" in the NBA.
"Just set that hard screen and roll to the basket. You got this," a fan tweeted.
Throwback footage of Green briefly playing football received an even harsher fan response, and tipped the scale in the NFL vs NBA debate in favor of NFL players.
Green ran a few informal plays during what appeared to be a spring Michigan State practice.
He jumped the snap in one video, and was beaten by a much smaller defender in another.
"Imagine being a 'bully' type player in the NBA, but getting stone-walled by a collegiate corner," one fan tweeted.
"He found out real quick that the gridiron is real different than the basketball court," a second fan posted.
The 6ft 6in and 230lb Green had a clear size advantage on his defender.
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But speed was missing, as was necessary side-to-side movement and finesse.
"LOL," one fan posted.
"Man got jammed up by a dude 100 lb lighter. I rest my case," a second fan tweeted.
Steph Curry as an NFL wide receiver is an interesting thought.
LeBron James as a pro tight end could have been a real possibility.
A leaner Watt might have been able to be an NBA forward.
Even Patrick Mahomes considered playing MLB before devoting his athletic career to the NFL.
But Green clearly looked overmatched while informally playing just a few downs of practice football.
It was an easy win for the pro-NFL crowd in the football vs basketball debate.
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"I don't think 30 NBA players would survive the physicality (of) an NFL training camp," one fan tweeted.
The NFL vs NBA debate is clearly just beginning.