In the case of Leonard Peters, they are probably right. His first choice was the no less physically demanding sport of American football. He has already been there, done that and got the breathable, Coolmax yarn playing jersey.
However, having since opted out of the game in which he made his name, first as a college football star at the University of Hawaii, then as an exotic addition to the playing roster of the Chicago Bears, he is now trying his hand at rugby.
His rise has been steep. It is just five months since he was first encouraged to pick up a rugby ball, yet he will already be playing his second international competition with the USA sevens side when they kick off the second leg of the IRB series in South Africa today.
Any opponents planning to pick him up on his style choices, such as the black nail-polish on his thumbs, would be better advised to think again.
He may be a rugby novice, but his skills on defence are already “beyond exceptional”, according to his coach Al Caravelli, which is a relic of his days playing as a safety in the NFL. It was the destructive side of rugby which first attracted him to the game.
“I was done with the NFL and coach Al gave me a call to see if I wanted to give rugby a try,” recalled Peters, 27. “He said that there was a lot of running and a lot of hitting so I said, ‘OK, sign me up’. It looked fun to me so I wanted to see if I could pick it up.
“For our team there is not a lot of money in it, but for some of the others there is. I didn’t do it for money, I wanted to do it to learn a new sport.”
Having been pitted in a group containing the world champions Wales, as well as the resurgent New Zealand side who won the opening leg of the series in Dubai at the weekend, the US face a tough task today.
For Peters, the last match in the group, against Samoa, carries the most significance. Peters was born in Fagaalu in American Samoa to Samoan parents, who moved to Hawaii when he was nine.
He has not forgotten his roots, as evidenced by the fact his body is decorated by pe’a, or traditional Polynesian tattoos. The masterpiece has taken 179 hours so far, and is still far from the finished product.
“Each symbol represents a generation of my family,” said Peters. “I am not finished, there is still a long way to go.”
Then there is the black nail varnish on his thumbs. Nothing to do with his Pacific heritage this time, but a reminder of his gridiron days when he and his teammates were signing autographs for a group of sick children.
“One of the children had cancer,” added the 6ft 1in Peters, who scored a try on his second day as an international rugby player at The Sevens on Saturday.
“At eight-years-old he was going to pass away. We were trying to sign autographs for them but they were very, very shy. I saw the mother’s nail polish on the stand, so I asked him if he would prefer to paint my nails.
“From then on, he started to talk to us and he painted my nails. Now I always paint them to remind myself how lucky I am.
“When you are eight-years-old and you are going to pass away from cancer, it shows that us people who run around playing football are extremely fortunate, even if we do get some nicks and dings.
“If I’m sore or I don’t want to practice or I’m having a bad day because I don’t have enough money for gas, if I wave to someone, or whatever I do throughout the day, and I see it I remind myself how lucky I am.”