BOSTON -- The fire that burns within Jon Lester is most obvious on game days, when his cheeks turn red and his eyes become steely as he looks toward his target behind the plate.

But those who are around Lester during the times that aren't so public -- be it in a weight room between starts or a backfield during Spring Training -- see every bit of that competitive fire and maybe more.

The pursuit of greatness never leaves Lester. The internal forces that drive him are probably the biggest reason his major bounce back from his first disappointing season last year was expected by his manager, his pitching coach and his teammates.

NLDS

If Lester was down on his luck last year, going 9-14 with a 4.82 ERA, he is again a top-of-the-rotation horse this year, one who will lead the Red Sox into their American League Division Series on Friday afternoon at 3 p.m. ET on TBS against the Tampa Bay Rays at Fenway Park.

"Until I came over here, I never really saw a guy compete every pitch, every out through pain, injuries or whatever like Jonny does," said catcher Jarrod Saltalamacchia. "He really competes. That's not easy to do, and he does it really well."

If you think Lester developed his epic edge as a professional, you'd be mistaken.

Long before the lefty ever collected a paycheck for playing baseball, he set a tone of self-motivation while pitching for his high school team at Bellarmine Prep in Tacoma, Wash.

"When our whole team was done with practice, he would stick around afterwards and [put in extra work]," said Rick Barnhart, Lester's high school coach. "You wouldn't know he was this standout talent, because he was always working harder than everyone else. That was always a pretty cool thing."

Barnhart, who still coaches at Bellarmine, doesn't try to pretend he molded Lester, who was drafted by the Red Sox. Instead, Barnhart still beams that he had the opportunity to coach him during those formative years.

"You didn't have to motivate him," said Barnhart. "He had good confidence; he had a little bit of fire. He could get a little bit upset at times, but in an appropriate way. You wanted him to have a little bit of fire. He never threw tantrums like some high school kids."

That resembles how Lester handled his tough season of a year ago. He didn't sulk or throw a tantrum. He gained resolve from it and figured out a way to turn it into a positive.

"Obviously last year was just horrendous all the way around," said Lester. "I know for myself I went home, usually I watch the playoffs if I'm at home or wherever I'm at, and didn't watch a game, turned it off, tried to kind of get my brain back on track. And to now be back to where we're at, not only be back, but to have the season that we did, you know, was obviously very gratifying for all of us in that clubhouse."

Clay Buchholz could see Lester had mentally flipped the calendar from 2012 just by watching him.

"Day One [of Spring Training]," Buchholz said. "That's basically how you are judged in this game, is by your numbers. You can't control all of them. But the feel from Day One in Spring Training was he took everything to heart and he obviously didn't think he had anything to prove to us. But he wanted to basically go out there and say, 'OK, well I forgot about that, but I'm going to use it to my advantage this year.' And that's what he's done."

Juan Nieves, Boston's new pitching coach this season, didn't take long to form an impression of Lester. And it's one that everyone from Barnhart to Terry Francona to John Farrell and many others have seen through the years.

"I saw a relentless competitor," Nieves said. "A very structured plan. Very consistent with his routine from the amount of running to the amount of throwing to how to prepare between starts, bullpen [sessions]."

That was all well and good, but Lester's rebound didn't just happen because of his strong mindset. There were also technical adjustments -- the type that established players aren't always comfortable making.

"He made some great alterations in his delivery this year," said Nieves. "In the sense of moving over, not so much to the first-base side, but he moved a little bit over to open up that down and away side. A lot of times he was so far over in the first-base side that pitches that the catcher caught down and away were called balls.

"It almost looked like he was coming from right-center field. So the angle of the umpire, he sees the ball. So he moved over a little bit and now the pitches don't come from right-center field. So it makes sense. And he ran with it and he used it. There were some mechanical things that we did, but they were not big mechanical things. They were alterations that put him in a better position to throw the baseball consistently."

There was one slump just before the All-Star break, but it turns out he just needed a little rest.

"Being a power guy like he is, and he leaves it all in the field, it's tough to crank it up every outing," said Nieves. "After the All-Star break, I think he recharged really well and here we go. His second half has been unbelievable."

For the most part, this season resembles many of the fine ones Lester has had throughout his career.

"I feel great," Lester said recently. "Just getting back to being me. I had it in the beginning of the year, hit a little bit of a bump in the middle and now I'm back to being me."

That means Lester is back to being an ace -- one the Red Sox just might be able to ride deep into October.

Perhaps another reason why overcoming a bad season was easier or Lester than others is because he knows about true adversity -- that kind that doesn't happen on a baseball field but from a CT scan that reveals chilling news.

Lester was 22 back in that rookie season of 2006 when he learned he had a form of cancer called anaplastic large cell lymphoma.

After coming back from that, Lester elevated his game as a pitcher and has worked equally hard off the field -- raising money for cancer.

Watching it all from Tacoma, his former high school coach has taken joy from his success and perseverance.

"You think, here's a kid who has the world by the tail, only to have the pegs knocked out from underneath him," Barnhart said. "But it's become a great story. Sometimes you think it's like a made for TV movie. This kid comes walking in and does so great and he gets knocked off his feet. Then he comes back. It's still a thrill every time we see him go out there. It never gets old."

Farrell, Lester's pitching coach from 2007-10 before returning to become his manager this season, has seen the evolution at the Major League level.

"Well, one, he knows himself much more clearly," Farrell said. "Things becoming more clear as far as gameplan and how he was going to execute it. He maybe isn't as reliant on someone leading him through the game as he is now recognizing certain situations and pitching through them by his own direction rather than taking the lead by [Jason Varitek], at the time. He's grown in that -- just through innings pitched and situations he's been thrown into."

And as you've probably gathered by now, there probably isn't any situation too daunting for Lester to handle.