HOUSTON — When Brad Peacock headed to spring training with the Houston Astros in February, he was so worried he wouldn't make team that he told his then-pregnant wife, Stephanie, that he might end up playing in Japan this season.

Instead of pitching halfway across the world, Peacock put together his best season and will make his first career post-season start when the Astros look to complete a sweep of the Boston Red Sox in the AL Division Series on Sunday.

When he takes the mound at Fenway Park for Game 3, it will be a culmination of years of ups and downs for the right-hander who saw this season as his final opportunity to prove that he could play at this level.

"That's what I kind of starting telling myself: 'This is my last chance. You've got to do it. You're healthy and just got to put some things together,'" Peacock said.

It's rare for a 29-year-old to completely reinvent himself as an athlete, but that's exactly what Peacock did. The result: a 13-2 record, with a 3.00 ERA for the AL West champions.

"I changed everything because what I was doing before obviously wasn't working," he said.

The extreme makeover began last year when Peacock was playing in Triple-A. He altered his arm angle and began pitching exclusively out of the stretch because he struggled to repeat his delivery from the windup. He saw some early success with the changes and then set out in the off-season to prepare like never before. It helped that it was the first time in a while that he had a regular winter after rehabbing from hip and back surgeries in recent years.

Stephanie, who has been with Brad for about a decade, still revels at the dedication he showed.

"I've never seen him prepare so much for a season as he did this off-season," she said. "He was religious about working out and eating right."

It paid off as he came to camp healthy and in great shape and turned heads from the moment he arrived, hardly looking like someone who had a career 11-17 mark of parts of five seasons.

Peacock easily made the team out of camp after worrying so much that he wouldn't, but there was still a part of him that wondered if he could perform at the level needed to play a role on a team that seemed destined for the playoffs.

That changed when he made his season debut with the bases loaded and no outs in the 13th inning of a game against the Seattle Mariners on April 5. The outing started out shaky when Peacock walked home a run to give the Mariners the lead. But he settled down after that and retired the next three batters, capped by two strikeouts to escape the inning.

George Springer hit a three-run homer in the bottom of the frame to give Houston and Peacock the win.

"I think that was a big confidence builder for sure," Peacock said.

And after the game Stephanie told her husband: "If you keep having games like this, you're going to put me into early labour."

Peacock continued pitching well out of the bullpen and when injuries began to decimate Houston's rotation manager A.J. Hinch looked to him to fill in as a starter. It was then that he really found his groove, winning eight starts between June 4 and Aug. 4 to help the Astros keep rolling despite the injuries.

"That stretch where he started for us ... is going to be what the story line is about Brad Peacock," Hinch said. "He came in and pitched extraordinarily well out of the rotation when our rotation was thin ... Brad Peacock was the consistent theme in that he won lot of games. He struck out a lot of guys. He pitched in a couple different roles. But that starting group in the middle of the season when Brad Peacock was stabilizing everything is why we were able to right the ship when things started to wobble a little bit."

When everyone started getting healthy, Hinch had to decide if Peacock should go back into the bullpen. He talked to the pitcher, and even though he knew that Peacock was notoriously low-key, he wondered why the pitcher didn't seem overly concerned about what his decision would be.

Peacock shakes his head and runs his hand over his short hair when asked about this.

"Just my situation, coming into spring I didn't know if I was going to make the team or not. I thought I was gone," he said. "So I'm just happy to be here and whatever they tell me to do, I'll do."

Stephanie has seen how much this season has meant to him, though.

"He may not really be a guy that shows much emotion with you guys, but let me tell you he's bursting with excitement on the inside," she said.

Said Peacock, on Saturday at Fenway Park: "Been humbled along the way, been injured along the way, and just makes it that much more special for me."

Peacock was on the team when the Astros made the playoffs in 2015, but was recovering from back surgery and was home in Florida during those games. So he became just another fan and headed to a local bar to watch with his buddies.

Flanigan's Seafood Bar & Grill in West Palm Beach is the kind of place that features $5.99 lunch specials and something called 'WayTooBig' sandwiches. It's also Peacock's favourite spot to hang at while at home, so it was the obvious choice to watch the playoffs.

As the Astros downed the Yankees in the wild-card game before taking on the Kansas City Royals in the ALDS, Peacock sat at Flanigan's sipping, on Crown Royal whiskey and wishing he was with the team.

"Obviously I wanted to be here and they sent me home. Which I understood because I wasn't doing anything here," he said. "(But) it was just weird. I wanted to be here. It was crazy."

On Sunday the man who was merely a spectator the last time around could play a huge role in helping the Astros advance to the championship series for the first time since 2005, when they reached their only World Series.

He's a father now after little Colton was born in June, and the baby boy will be there on Sunday wearing the tiny Peacock jersey Evan Gattis bought him. Peacock credits fatherhood as another reason for his turnaround in a season where he's made 21 starts and 13 relief appearances, striking out 161 in 132 innings.

"Just having that kid, just knowing I've got to take care of him now," he said. "So I think that's a big thing, just trying to concentrate out there and I ... think about him out there. Like: 'Gotta do good for him.'"

And among his biggest joys these days is seeing him smile. So a final question for Peacock is what's better, seeing the grin on his little face or striking out the side?

"Seeing the baby smile, for sure," he says before pausing for a second. "Maybe striking out the side in the playoffs. I don't know."

Then Peacock, who never expected to be here, flashes a huge smile of his own.