"It was pretty straightforward," the gifted left-hander told The Associated Press in a story that ran on Friday. "I just walked out of the hotel, got in the car and left."
With that, Chapman had left his room at the Domina Hotel in Rotterdam last July and was separated from his parents, sisters, girlfriend and an infant daughter he's never seen.
That eventually took him through stops in Spain and Andorra in the Pyrenees, where Chapman established residency so he could become a free agent and not be subject to the First-Year Player Draft -- which would've happened if he were to become a U.S. resident.
Now, he's in New York, where he watched the American League Championship Series between the Yankees and Angels and did a wide-ranging interview at The AP office on Thursday.
Chapman, who stands a lanky 6-foot-4 and throws a 100-mph fastball, has drawn interest from the Yankees, Mets, Red Sox and Tigers, among others, and figures between $15-50 million have been mentioned for his services.
Chapman said he compares himself mostly to Randy Johnson, affirmed that his fastball is his best pitch, added that he also throws a curveball, slider, changeup and splitter, and he admitted the main thing he needs to work on is his control.
The 21-year-old also said, "I don't like the cold." But he braved it out so he could watch the clinching Game 6 of the ALCS at Yankee Stadium.
"I would think of what pitch would I throw this batter and things of that sort," Chapman told The AP. "There were many that were the same as what I was thinking. There were a few that weren't, but not all pitchers are the same and some think differently. I can maybe depend on my fastball a little more than some other pitchers."
Chapman gained attention during the World Baseball Classic in March, which saw him finish with a 5.68 ERA in 6 1/3 innings -- striking out eight and walking four -- after pitching well against Australia but struggling against Japan.
After the Classic, The AP wrote that Chapman contacted a friend from Cuba before the World Port Tournament -- an event that included the national teams of Cuba and the Netherlands, and Japanese and Taiwanese teams with mixed Minor Leaguers and industrial-league players -- about possibly defecting.
Afraid of leaks, he didn't tell any of his family members, not even his pregnant girlfriend.
Chapman said he spoke by phone with his family the day after, and he's spoken with them frequently ever since. His daughter, Ashanti Brianna, was born a few days after his defection, The AP wrote.
"I only spent one hour at the hotel thinking about what to do," Chapman said. "I made the decision, stepped away from the hotel and got into the car. Everything was planned from a few months before the tournament. I discussed the idea with a friend and made the decision to do it -- never thought about doing it during the Classic. It was something that I was seeking before the Classic, but I didn't want to do it in the Classic."
Now, he knows there's work to be done if he's going to make it all worthwhile and pitch in the big leagues.
"I feel that I need to improve a bit my control, but not so in the execution of the pitches," Chapman said. "I feel that I have sufficient repertoire to pitch in the Major Leagues. I don't foresee problems to play in the Major Leagues."
Chapman was a first baseman until he was 15 or 16, when a school pitching coach suggested he give the mound a try. By 2005, he was 18 and pitching for the Cuban national team, according to The AP.
Baseball experts say Chapman needs some seasoning before he's ready to pitch in the big leagues. But the Cuban pitcher with a golden arm has no problem with paying his dues before finally living out his dream.
He's done so plenty of times already, anyway.
"If a team wants me to go to the Minors to get ready and prepare, that's what I'm going to do," he said, "and I will show that I should be pitching in the Major Leagues."
Chapman's agent, Edwin Mejia, told Yahoo! Sports that he'd like to get a deal done soon.
"If the right offer comes in, it'll get done," Mejia said. "I'm not looking to prolong this. It comes down to what's best for Aroldis, and the teams' offers have a big say in what's best. Are we prepared to wait until whatever? Of course.
"To be honest, it's easy to be calm when you have a kid with this skill set."
Alden Gonzalez is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.