Leonard Fournette is the American football player that ESPN writer Kevin Van Valkenburg says is a superior athlete to any New Zealand rugby player.

ESPN senior American football writer Kevin Van Valkenburg has attracted vitriol after declaring that the USA would dominate world rugby if the NFL's top talent were to be made available.

In a tweet, Van Valkenburg said: "Briefly watched college rugby today while getting a hair cut b/c they wouldn't turn on golf.

"Conclusion: If you gave me a year, Urban Meyer, Zeke Elliott, JJ Watt, Leonard Foutnette & an NFL practice squad, the US would so thoroughly dominate rugby, other countries would quit."

When Twitter poster John Caulfield replied: "I seriously doubt that. A serious insult to top rugby playing nations such as NZ. A lot of subtlety missed here," Van Valkenburg said: It's a serious insult to think any of those NZ dudes is as good of an athlete as Fournette".

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Fournette, 23, is a running back for the Jacksonville Jaguars in the NFL.

KEVIN C. COX/GETTY IMAGES Leonard Fournette dives into the end zone for a touchdown.

Former Wales great and now BBC broadcaster Jonathan Davies had a one-word reply to Van Valkenburg. "Clueless".

Welsh commentator Simon Thomas was also dismissive. "A statement which is both ignorant and arrogant - not a great combination," he said.

Further on in the debate, Thomas queried on how the NFL players would do without their pads. He said that with their heavier average weights, "NFL players wouldn't be able to last 15 minutes in rugby, where the ball-in-play time is so much higher."

Sonny Bill Williams was introduced to the debate. Tweeter Nick Mackay said SBW was twice the player that Fournette was. To which Van Valkenburg asked: "Twice?". Mackay replied: He's way bigger and just as strong. Has won World Cups in two different sports, was the NZ WBA boxing champ and has a lifetime 7-0 record as a pro, runs the 100m in 10.5. And he can pass and kick." Mackay later admitted he might have got SBW's 100m time wrong.

Even a politician waded in. Senator Neale Thomas, who sits on the Labour Panel in Dubin, said: "Ah here, I love NFL but that's a ridiculously ignorant comment. Watch a full 80mins of top class rugby with guys who've been playing since they were kids & comment rather than a bit of a US college game with guys who may only have played for a year or two."

When Irishman Brendan Kelly advised Van Valkenburg to check out the best rugby teams - New Zealand, Australia and Ireland - saying the standard among US college teams was aeons below international standard, Van Valkenburg did relent a little.

"No chance a team of US studs would dominate. But our best football players would absolutely be successful if given time to learn the nuances."