CHICAGO (AP) The story of how Jake Arrieta transformed himself from one of baseball's most thoughtful pitchers into one of the hottest is the opposite of an overnight sensation.

The Cubs right-hander didn't wake up one morning and discover a magic grip or even find an extra 5 mph on his fastball. The closest he came to an epiphany was two years ago as he shuttled between the big league Orioles and their minor league affiliate in Norfolk, Virginia, wrestling with the possibility that his talents were used up.

Arrieta was 27.

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''There was this moment in Triple-A where I didn't want to play anymore,'' he said. ''This game beats you up, makes you feel sometimes like you're not good enough. For a couple months, I was in a mindset, `This is hurting my life off the field and I'm way too worried about this game. It's affecting me, mentally, way too much.'''

Up close, it's easy to see the intensity that's unnerved National League hitters for the better part of two seasons. Just recalling that time, though, puts Arrieta on edge; he leans in and fidgets with the buckle on an expensive watch.

''I was tired of the frustration, tired of this thing I couldn't control. ... And you know what, I talk to my wife about the same stuff every so often, even now. Stuff like, `What are we going to do, what kind of business could we start when we're done playing?'

''The big difference,'' he added a moment later, ''is that those were serious conversations a couple of years ago.''

Instead of giving up, Arrieta doubled down. He treated the five days between starts getting ready for opponents the way an NFL team would.

He broke down the process familiar to every pitcher at every level of the game - preparation, scouting, mechanics, delivery, release - and made himself stronger in every phase. Arrieta's daily workout regimen was the subject of clubhouse envy when he arrived in July 2013. Soon after he began working with Chicago pitching coach Chris Bosio, so were his off-day sessions throwing on the side.

''I remember going over the scouting reports,'' Bosio said, ''and thinking it had a lot to do with how he was attacking hitters. The league was hitting .460 on his first pitch, something like .570 when he got to a 1-1 count. ... With Jake, we started on the sequencing stuff - what to throw when - and he was tireless. He'd practice it over and over in the bullpen, so he owned it before he'd use it in a game.''

The resulting confidence eased Arrieta's fixation on mechanics. He refined every aspect of his delivery from shoulder turn to fingertip release, then repeated it until that, too, was second nature. Gradually, his fastball got faster and his breaking stuff a lot filthier.

And his stats got a lot better, a huge reason the Cubs are solidly in playoff contention. Arrieta leads the majors with 18 wins, and ranks near the top with a 2.03 ERA while averaging more than a strikeout per inning.

Long before his Aug. 30 no-hitter against the Dodgers turned every start into must-see TV - Arrieta next pitches Thursday night at Philadelphia - and even longer before he elbowed his way into the Cy Young conversation, Arrieta had already made believers of the guys he played alongside and against.

''Even when he makes a mistake, it's a 97 mph pitch with cut down the middle,'' Arizona's A.J. Pollock said. ''It's a different mistake.''

This was right after Arrieta yielded just four hits in a 2-0 win against the Diamondbacks in his first start since the no-hitter. Two of those came in the first inning. Someone asked whether he was relieved the pressure of another no-hitter was off so soon.

''I would have preferred to not give up any hits,'' Arrieta said earnestly. ''But those guys are good.''

Even so, Arrieta had all the answers. He throws his changeup, on average, less than 10 percent of the time, but after watching the Diamondbacks sit on his fastballs, he threw the changeup in three tight spots in the fourth inning to strike out Paul Goldschmidt and Jarrod Saltalamacchia and fool David Peralta into a groundout.

An hour after that, the Chicago locker room is nearly empty and Arrieta is considering a final question: How much better can he get? It's something he's thought about a lot. Every part of the process, he said, is still open to review.

''Nobody can repeat their delivery perfectly for 120 pitches,'' he said. ''But the closer you can get, the better you're going to command the ball from start to finish. At the end of the day, good stuff is great, velocity is great, good breaking stuff is crucial to having a lot of success here.

''But commanding the baseball,'' Arrieta said finally, ''is the most important variable in pitching.''