CLEVELAND — Ten years ago, it seemed like a prophecy whose fulfillment would prove inevitable: Rick Porcello, staff ace, Game 1 postseason starter.

By 2006, Porcello had established himself as an elite amateur talent. That summer, in the East Coast Pro Showcase of top high school talent, he stood out on a Northeast team that featured a number of future first-rounders, including Matt Harvey.

“Something I’ve always tried to make a point of doing is catching these guys myself in the bullpen. It’s an interesting perspective,’’ recalled Red Sox Northeast scout Ray Fagnant, who coached Porcello on that showcase team. “I just remember Porcello vividly standing out. He’s one of those guys who, the last 2 or 3 feet, the ball would just explode on you. You’d catch a fastball and say, ‘Wow, I was a little late on that.’ It had that glove travel at the end. He really stood out. His calm and confidence, he was just different.’’

The Tigers agreed, viewing him as so developed that they took him with their first-round pick in 2007 and signed him to a major league contract — a $7.28 million bet that he’d be in the big leagues for good within four years.

“We thought he was going to be a No. 1 starter at the big league level,’’ said Red Sox president of baseball operations Dave Dombrowski, the Tigers’ president/CEO/GM when Porcello was taken.

That vision has now been fulfilled, in a year where Porcello is a short-list Cy Young candidate after going 22-4 with a 3.15 ERA while leading the majors with 5.9 strikeouts per walk. Yet the fashion in which he’s arrived at his long-anticipated destination runs counter to what the baseball world anticipated.

“When we drafted him we thought of him as this flamethrowing top-of-the-rotation type guy,’’ said Dombrowski. “What he’s done is he’s adjusted his game.’’

Porcello has done so under some of the most challenging circumstances imaginable. Dombrowski and the Tigers (particularly manager Jim Leyland) thought highly enough of Porcello that, after just one season of pro ball spent in high Single A, they let him jump into the big league rotation as a 20-year-old for the start of the 2009 season.

He impressed as a rookie, posting a 14-9 record and 3.96 ERA, but he did so while throwing little except low-to-mid-90s two-seam fastballs. He’d never learned to pitch in the upper minors, making his crash the following year — a 4-7 start with a 6.14 ERA through 13 starts that resulted in a demotion — almost inevitable.

A demotion can overwhelm a young pitcher after a fast track to the big leagues. Porcello was mature enough to ensure that wasn’t the case. He took the lesson of Roy Halladay to heart, recalling that the Blue Jays once demoted the righthander from the majors to high Single A, and concluded that his setback need not represent a dead end.

“Obviously, the disappointment in my performance leading to me getting sent down is something that didn’t sit well with me,’’ said Porcello. “[But] I remember after the initial day or two back down in Triple A, reorganizing my thoughts and trying to think of the adjustments I had to make to get back to the big leagues, and not just to get back there but to go to another level and improve.’’

Porcello used that time to refine his delivery, to add to his arsenal, and to regain his bearings. When he returned to the big leagues after a four-week demotion, he pitched well (4.00 ERA in 14 starts), and became a stable mid-rotation contributor to the Tigers through 2014.

It would seem natural for Porcello to use that prior struggle to inform how he approached his poor start to his Red Sox career last year, when he finished July with a 5-11 record and 5.81 ERA before landing on the disabled list. Yet Porcello saw no parallel between his early-career circumstances and his struggles as a 26-year-old in Boston.

“That [2010] experience had really no impact or provided no benefit for me last year,’’ said Porcello. “The circumstances were completely different so it felt completely different. When you’re 21 years old and you struggle, it’s to be expected. When you’re traded for an All-Star-caliber outfielder [Yoenis Cespedes], you come over to a team that has high expectations and are expected to be a productive member of that, you don’t have that same leeway.

“I couldn’t really sit back and think, ‘This has happened to other guys.’ It was like, ‘I had a really good thing going [in 2014]. What the hell happened?’ ’’

Yet there was a common outcome between Porcello’s time on the DL — and minor league rehab assignment — in 2015 and the demotion of 2010. He used the time to get better. He ironed out delivery consistencies that came from an overreliance on his four-seam fastball, and with his arm slot back in its ideal place he unlocked the ability to execute a complete arsenal — two- and four-seam fastballs, curveball, cutter/slider, changeup — while attacking the strike zone.

In so doing, he now stands as a radically different pitcher from the one-pitch thrower who reached the big leagues at 20. Likewise, he’s radically different from the projected vision of his future as a prototypical power pitcher. But he is nonetheless a frontline starter thanks to his ability to show elite command, mix pitches, and exploit opponents’ weaknesses.

“You usually see flamethrowers that are No. 1 type guys, but that’s not always the case,’’ said Dombrowski. “Look at Greg Maddux. He wasn’t a flamethrower but one of the best in the game, a Hall of Famer . . . [Porcello’s] command is phenomenal. I don’t think we could have predicted the command at this point. He’s continued to develop.’’

In so doing, the righthander has finally performed to — and arguably beyond — any expectations that greeted his entry into pro ball 10 years ago. His Game 1 responsibilities against the Indians serve as a form of validation.

Yet while Porcello derives satisfaction from having earned his team’s trust, and having contributed to its success, he likewise views his new role as a staff ace not as a long-anticipated destination but instead as a new beginning.

“You can’t really dwell on those sort of things or, for me, rest my hat on the fact that I’m pitching to that caliber . . . It’s kind of an uneasy feeling,’’ said Porcello. “I don’t want to get complacent and be like, ‘I’ve done this now. I’ve arrived. Now I can stop.’ As appreciative as I am of that recognition, I can’t allow myself to think like that. I would maybe be overlooking things that I really need to stay focused on and that have allowed me to be sharp up to this point.’’

That mind-set has driven Porcello in a way that has allowed him to reach this point, and that the Sox hope will allow him to anchor their hopes of a run deep into October.

Alex Speier can be reached at alex.speier@globe.com. Follow him on twitter at @alexspeier.