And now, whenever he gets in a game, the 33-year-old rookie will know that his journey has been worth the wait. Castillo, who was promoted to the Orioles on Tuesday, is excited to finally step on a big league mound.
"It's a great feeling," he said. "It's been a long time since I came to this country in 1994. All those years of playing in the Independent League and I finally worked my way out. I've reached my dream."
That dream, however unlikely it may have been, came close to collapsing on several different occasions. Castillo struggled through the lower levels of Tampa Bay's organization for seven seasons before falling out of organized baseball. And still, he toiled, trying not to gauge the odds stacked against him and finding support from his wife when times got tough.
"I considered quitting one time," he said. "I was in Spring Training with the Cardinals in '03 and I got released. I had had a great Spring Training, and I told my wife, 'That's it for me.' She told me, 'No, keep going. You're still young.' And then there's the year I got hurt, too. After surgery, it was really tough. I thought I was never going to come back."
Castillo wound up getting ligament replacement surgery on his right elbow in 2004, and he said that was likely the turning point in his career. From there, it was all about getting healthy and proving himself all over again. Castillo went to the Mexican Winter League and earned a notice from Baltimore, which made his year by bringing him to Spring Training.
He earned a spot at Triple-A Norfolk from there and didn't look back until he got the news of Tuesday's promotion.
"I was suspicious," he said, recounting one of the momentous events in his life. "I couldn't believe it when [Norfolk manager] Gary Allanson told me I was going to come up here to Toronto and join the team. I was very excited. It's an amazing feeling [but] I think my wife was more excited than I was. She couldn't stop crying. She knows what I went through."
"He's 33 years old," added manager Dave Trembley of the unlikely story. "It's the first time he's been to the big leagues, but he played for a long time in the Independent Leagues. He defected from Cuba. He's very thankful for the opportunity."
Castillo, who will likely be used as a situational southpaw, said that he'd take his journey all over again. He also admitted that it took him far longer to reach the big leagues than he originally expected and was glad to be able to share it with his family.
"It's funny, because I defected to Windsor, Ontario," he said of his life-changing decision. "So it's funny that the first call up that I get is in Toronto. My sister's still in Cuba, and she hopefully will be here in September. But my parents came two years ago, finally. We're a very close family. It was tough for them and it was tough for me to be here by myself.
"I was young and it was tough, but I don't regret it. I think I made the right decision."
Spencer Fordin is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.