As he was growing up in Venezuela, Brusdar Graterol said people in his hometown began taking notice of his strong arm when he was 5 or 6.

"Playing in the neighborhood with the other kids, throwing around stones and stuff like that, people were like, 'You throw hard,' " Graterol said through an interpreter. "I always knew I was going to throw hard."

Throwing around stones? Those had to hurt the other kids, especially coming from an arm of someone who would go on to throw 100 miles per hour.

"They stopped playing with me after I started throwing stones," Graterol said.

The natural talent has always been there for Graterol, who Twins fans hope can make an impact in the postseason with his flame-throwing arm.

But Graterol is only 21. If he was going to harness the potential in his arm and become a consistent major league pitcher, he had to develop discipline, a hard work ethic and learn how to carry himself off the field. He found his model in one of his teammates — Jose Berrios.

"He became my favorite player three years ago not because of all the work he puts in the gym and on the baseball field but the things he does off the field with his family," Graterol said. "How he carries himself, and so I want to imitate that."

Graterol has even adopted and adapted Berrios' nickname, La Makina, or "the machine" (with Berrios replacing the "k" in the Spanish word "maquina" to signify strikeouts). Graterol calls himself "El niño makina" (boy makina).

Berrios relishes being Graterol's mentor.

"It's amazing, meeting people like him," Berrios said. "Now I have the opportunity to bring him my experience, my day-by-day. He's in the same clubhouse now and we're teammates. I've always heard about him. He's got really good stuff, but I never had the chance to see him pitch. It's amazing the things he's doing out there."

Graterol, who made nine starts for Class AA Pensacola, has made seven relief appearances for the Twins since coming up at the beginning of the month and has allowed four runs in 7⅓ innings. He's one of a handful of relievers, such as Devin Smeltzer and Cody Stashak, who manager Rocco Baldelli has been trying to ease into big league moments.

"When a guy first gets called up, it's nice to get them some lower-leverage appearances before you shuffle them on in there if you can do it," Baldelli said. "Doesn't always work like that, but I think we're not afraid to challenge our younger players. If we think someone can handle it and we think that they have the ability, I see no reason why we won't turn to them in some important spots. We've already done it."

Graterol said adjusting his mind-set to being a reliever instead of a starter hasn't been too hard, and, of late, Baldelli has been bringing Graterol in with men on base so Graterol begins throwing from the stretch.

"When they told me I was going to become a reliever at this level, I just prepared my mind to be ready for that," Graterol said. "I don't think about it as much different."

If he has any questions, Berrios is there to answer.

"Sometimes I run out of questions," Graterol said. "But he helps me all the time and it's good to have him close and every time I have a concern. I know I can just look to the left and he's going to be there."

Said Berrios: "I always tell him, be you. You have great stuff. You are great. You are the machine, like you say. The other thing is have fun, believe in yourself, and that's what he's been doing so far."