Gatlin said no such thing. The "warning" is strictly the language of the writer and the headline writer. Here's what Gatlin said, in case somebody didn't read the link you posted:
"I don't turn up to races trying to be second and third, I train to go out there and run fast and be dominant in the race," he said. "You want a mixture of great athletes, you want to come to an event where you really don't know who's going to win. You want to go out there and have a really good dogfight. You've got to let him [Bolt] do what he does and I'll do what I do. When we meet each other, may the best man win."