OAKLAND -- From substitute teacher to starting southpaw for the Oakland A's, Bobby Cramer's path to the big leagues was unorthodox to say the least.

The A's on Friday promoted the 30-year-old hurler from Triple-A Sacramento, and he will make his Major League debut on Monday in Kansas City in place of recently demoted Vin Mazzaro.

"I love competing," Cramer said. "I was released in the spring of '05 and didn't play [professionally] for two years. I had to play Sunday ball just for fun. I just need some type of competition in my life."

Drafted in the 38th round of the 2001 First-Year Player Draft by Seattle, Cramer underwent Tommy John surgery in '02 before making his professional debut with the Tampa Bay organization in '03.

Once he walked away from the game in '05, Cramer took a job in Shell's pipeline division, working in maintenance and safety. After Shell let him go, Cramer started teaching at a continuation school in Orange County, Calif., where he used to substitute.

"Math was probably my worst subject in high school," Cramer said. "I basically had to take the book home and stay one section ahead of the kids every night and work out the problems myself and take tests and relearn it all, just so I could explain it to them and sound like I knew what I was talking about."

But the A's gave Cramer another shot in 2007. He pitched for Class A Stockton and Double-A Midland, going a combined 9-2 with a 2.77 ERA in 21 appearances (15 starts). The next season, Oakland invited Cramer to Spring Training, but a balky shoulder ended his first tenure with the club.

Once Cramer's shoulder healed, he signed with the Orange County Flyers of the independent Golden League on the advice of his agent. Cramer said he had conversations with a few clubs during the 2008 season, but that no one was interested enough to offer him a job until the A's re-signed him before the '09 campaign.

Cramer then went 5-5 with a 3.88 ERA across three levels of the Minors, including Triple-A, before the A's lent him to the Tigres de Quintana Roo in Cancun, Mexico, for the 2010 season. After Cramer went 13-3 with a 2.95 ERA, he was added to the Triple-A Sacramento roster on Aug. 5. He went 2-2 with a 1.94 ERA in seven starts with the RiverCats.

"I don't base my outings on how I'm doing against that current team," Cramer said. "I try to gauge it on what I think I would have done against a big league team that day. I felt like I had good enough stuff [in Mexico] that I would have got people out in Sacramento or maybe even here. To stay down there for the whole year was a little frustrating, but in hindsight, it worked out."

When comparing the Mexican League competition to its American counterpart, Cramer said the pitching was akin to Double-A quality, the hitting to Triple-A and the fielding to Class A. Cramer also has plenty of experience in the Latin American winter leagues, as he has played in Puerto Rico, Mexico and the Dominican Republic.

"I'm not going to light up the radar gun. I'm not going to blow anybody away. I don't have electric stuff," Cramer said. "I'm a control guy. I try and keep the ball down, move it in and out, try to change speeds. I'm your typical crafty lefty."

Sounds a bit like Dallas Braden, no?

A's manager Bob Geren said Cramer's position within the staff will be evaluated after his start on Monday. Since the A's have an off-day on Thursday, they could elect to skip Cramer's spot in the rotation.

"It's a good story on a personal level," Geren said. "But on a baseball level, he's been [Sacramento's] best pitcher, and that's what we tend to do. If we need a spot, we go with who's the hottest, and he's been throwing the ball well."