RIO DE JANEIRO -- A decade ago, when Olympic sprinter Justin Gatlin was banned from his sport for a doping violation, he thought about spending his time playing professional football.
He tried out with the Houston Texans. And then with the Tampa Bay Buccaneers.
Gatlin quickly learned that it takes more than just world-class speed to make it in the NFL.
"It's so tough," he told The Associated Press. "I would say that how track and field is built without a union and it's a dog-eat-dog world, that's how it is to get into football. It's the same thing: a dog-eat-dog world. I respect all those athletes who are trying to try out for teams.
"They're judged not only by their athleticism," he said, "but if they even need them."
But what if you did judge NFL players and Olympic athletes only on athleticism? What if you were to throw out everything but the barest of statistics - speed, strength, vertical jump?
Who would be the superior athletes?
Of course, such a simple question has no simple answer. Not even those involved in the debate seem willing to hazard a guess, perhaps trying to ensure that their separate sports receive their own due.
Make no mistake: They are separate. But comparing them - sprinters to NFL running backs, linemen to weightlifters, wide receivers to high jumpers - is at least an entertaining endeavor.
"Speed comes in all different kinds of forms," said Gatlin, the reigning 100-meter Olympic bronze medalist. "All the fast guys you can think of, we all can run - let's say we run 9.99 (in the 100). We all have different strategies and forms to run 9.99. We all get to the same point in different ways.
"For a football guy, he's explosive and powerful," Gatlin said. "So if we race in the 40 or 60 or something, I don't know exactly how it would turn out. They might have more explosive speed from the line than I would, because even though I'm a fast guy at the start, I might have to build my speed up because that's how I'm programmed to do it."
Rarely do NFL players run more than 40 yards at a time, which is partly why times for 40-yard dashes are such common descriptors of speed. The record at the NFL combine was 4.24 seconds in 2008 by Chris Johnson, the former Pro Bowl running back who once boasted he could beat Usain Bolt in a race of that distance.
Gatlin said he's run unofficial 40-yard times between 4.12 and 4.35 seconds.
"I would win on the tail end," he said, "but it would be good competition on the front end."
Trying to compare NFL linemen to weightlifters may be even more difficult.
The lifts done by football players tend to be the more common strength-training lifts such as the dead lift and bench press. In fact, the biggest strength indicator at the NFL combine is the bench press, where rookies-to-be are required to lift 225 pounds as many times as possible.
The record is 49 repetitions set by Redskins defensive tackle Stephen Paea in 2011.
"That's a worthy feat, so I can't make light of it," said Kendrick Farris, the lone men's Olympic weightlifter representing the U.S. at the Rio Games. "But if weightlifters focused on that particular exercise with that load, the results would be quite interesting."
Instead, they focus on two particular lifts: the snatch, in which the weight is lifted from the ground to overhead in one movement, and the clean and jerk, where the bar is lifted in two movements. The combined results of the lifts determine the placement in a competition.
Being strong is important, but technique is also a significant factor.
"If football wasn't my thing, I would probably pursue strongest man," Paea said, "because I've got the lower center of gravity, things like that. I'm pretty strong on the squat, too.
"Weightlifting, you've got to give it to them," he added, "but if it comes to like overall running, all those conditioning (aspects) with it, we'd probably give them a good run for their money."
How about comparing vertical leaps among NFL players to Olympic high jumping? Well, it's similar to weightlifting in that athletic ability and technique go hand-in-hand.
You won't see a wide receiver flopping backward over a bar while hauling in a touchdown pass.
"I know a couple of people in college who did the high jump and they have some springs, man," said Chiefs wide receiver Chris Conley, whose 45-inch vertical at the 2015 NFL combine is the record.
"They can definitely jump a lot higher than me. It takes a lot," he said. "Technique is the most important thing. At some point there's God-given talent, but when it comes to that level of jumping, the difference between the world record and that level of medaling is all in the details."
One thing all those athletes can agree on? They love watching their counterparts compete.
"We have a lot of swimmers from (my alma mater) Georgia that qualify every year and I know some of them," Conley said. "I like to watch because it's my background, but I also know people there as well."