Justin Gatlin, USA Track Legend, Training For Record 40-Yd. Dash, Eyeing 4.19

Justin Gatlin is officially retired from competing, but that doesn't mean the USA track legend's done running ... in fact, the Olympic gold medalist is currently perfecting his 40-yard dash, and believes he can run a blistering 4.19 seconds!

"The project is Project 40. I ran a 4.2 yesterday, first day of practice," Gatlin told Michael Babcock on the "TMZ Sports" TV show (airs weekdays on FS1).

FYI, the fastest 40 ever electronically timed at the NFL Combine was 4.22 by John Ross in 2017. Chris Johnson holds the second-best time at 4.24.

Justin believes he can beat that time by a substantial margin.

"I'm thinking a 4.19. I definitely can dip under the 4.2s, for sure!" Gatlin said confidently.

Ultimately, Gatlin wants to train athletes to be quicker on the field or court.

"I've been training since I've left the world of track and field and I have an idea that I wanna be able to do speed agility training or professional athletes, being football, baseball, basketball, that's why we're here."

Justin says they're often a debate about who's faster ... and while he does want to rep for the track athletes, he also wants to help out other pros in different sports.

"There's a lot of talk about track and field athletes and football players, who's faster and I said you know what, this is what we work on. We work on speed constantly and I wanna show the world that we understand speed, we're the king of speed but I also wanna teach speed to other athletes that want [to learn.]"

Justin sure sounds like someone who still has the competitive juices flowing ... so we asked him if there was a chance he could make a comeback competitively, despite being 41 years old.

"Let's say if I get myself back into shape and say 'Hey, you know what? I wanna get back in track and field,' especially Olympic year coming up, it's not far-fetched."

"I've been away from the track, what, I retired in 2021? I'm not that far off. I think that if I wanna come back, I can make that Olympic team for sure."

There's more with Gatlin ... including whether he'd be down to race Tyreek Hill -- "Cheetah" -- who most fans believe to be the fastest player in the NFL.

So, would Justin race Cheetah? Damn straight.

"I think [Tyreek's] a remarkable athlete. He has a big background in track and field. He grew up running track and field. He still uses track and field workouts to make sure his speed on the football field is superior."

Gatlin continued ...  "And when it comes to me racing Tyreek, holla at me in about eight weeks. I'll be ready for you, man. If you want that, I can give you that smoke.

We also talked to Justin about Noah Lyles ... both his epic performance at World's and his shading of NBA "world champions!"