By Wendy Thurm

SAN FRANCISCO -- He stands tall on the mound, the ace of his team's pitching staff. His left arm is a powerful weapon, spinning fastballs, curves and change-ups past hapless opponents. Over the last three seasons, he struck out more than 23 percent of the batters he faced and allowed fewer than three-and-a-half runs to score every nine innings he pitched. He dominates his division, the NL West.

He grew up in modest surroundings with a strong faith in God instilled in him by his mother. He was a highly touted pitching prospect in high school, and turned down a baseball scholarship to a top school in his home state to enter the draft. He debuted in the majors just after turning 20. He married his high school sweetheart.

Clayton Kershaw or Madison Bumgarner?

Yes.

He won two World Series rings by the time he turned 23? 

Bumgarner. The other lefty ace in the NL West.

Kershaw owns the two Cy Young awards, the pitching Triple Crown from 2011, and a new $215 million contract with the Los Angeles Dodgers that's made him the highest paid pitcher in baseball history. He also owns the unofficial title of best pitcher on the planet.

Bumgarner owns the two World Series rings with the San Francisco Giants, a more modest $35 million contract (through the first year of free agency), and no less a desire to be the best pitcher on the planet. On Monday, he'll add Opening Day starter to his long list of accomplishments -- all before his 25th birthday.

Giants manager Bruce Bochy loves Bumgarner's drive and competitiveness. "He's a very focused pitcher with great stuff. He's young but continues to get better," the skipper said Friday evening before the Giants' exhibition game against the Oakland A's. "When you're competitive like Madison -- and have a fastball, curveball and slider that changes speeds -- you're going to pitch well." 

Bochy looks forward to watching Bumgarner battle against the best, especially Kershaw. "You're seeing two of the top lefties in the game. Kershaw's at the top but Madison is right there. Two big guys that can beat anyone with great stuff. Those two will match up for years and it will be great."

For his part, Bumgarner appreciates but isn't in awe of Kershaw's mastery. He looks forward to dueling the reigning Cy Young award winner as the Dodgers and Giants duke it out in the NL West.

"You want to pitch against the best. That makes it fun," Bumgarner said Friday evening at AT&T Park. "Those games are always a battle the whole way. When you take on the best starter, you find out what you're made of." But, Bumgarner continued, "I'm not trying to be better than somebody else. I just want to be the best I can be."

That best has been pretty good so far.

Bumgarner's started 115 regular-season games since his call-up in late 2009 and recorded 677 strikeouts against only 186 walks. Batters have hit only .239 against him in his career. Dating back to 2011 -- his first full season in the Giants' rotation -- Bumgarner boasts the fifth-lowest ERA in the majors (3.12) among pitchers with at least 85 starts, or three full seasons in their team's rotation. The guys with the four lower ERAs? Kershaw, Cliff Lee, Justin Verlander and Jered Weaver. Not bad company.

Despite Bumgarner's big frame -- he's 6-foot-5 and weighs 235 pounds -- he's not all about the fastball. Giants broadcaster Mike Krukow, a former starting pitcher, likes to talk about the evolution of a young ace from thrower to pitcher, from someone who knows mostly how to strike a batter out with heat, to a chess master who employs a full arsenal of pitches strategically and efficiently. It perfectly describes Bumgarner.

When he first broke into the Giants' rotation in 2010, Bumgarner relied heavily on his fastball, especially with his first pitch of an at-bat. Overall in 2010, Bumgarner threw his fastball 54 percent of the time to left-handed batters and 57 percent to righties, according to data collected and analyzed by BrooksBaseball.net. By last season, the fastball had taken a backseat to the cutter (sometimes called the cut slider) as Bumgarner's most frequently-used pitch to right-handed batters, followed by the fastball, curveball and change-up. 

I asked Giants closer Sergio Romo to compare his exceedingly deceptive slider to Bumgarner's cut slider. "You wouldn't think they'd be similar," Romo said, "if you look at us. He's a big lefty. I'm a smaller guy who throws righty. But our arm angles are pretty similar. We both just attack the zone."

Against lefties, Bumgarner's fastball is still king, and for good reason. He begins the pitch with his signature twist-at-the-hip and then unleashes the 92-mile-per-hour heat from a three-quarter release point. By the time left-handed batters pick up the pitch, it's too late to get good wood -- or any wood -- on the ball. Giants reliever David Huff, who is new to the team this season, couldn't stop marveling at how Bumgarner devastates lefties with his fastball: "He rears back and throws it. Against lefties, the ball is coming right at them, yet it's so deceptive."

And then there's Bumgarner's wicked curveball. Last season, left-handed batters whiffed on 30 percent of his curveballs. With two strikes, the whiff rate rose to 40 percent. It's no wonder that Bumgarner held lefties to a .201 on-base percentage in 2013.

Perhaps Bumgarner's most effective weapon on the mound isn't his fastball -- or his cutter, or his curve. No, what Bumgarner is best known for around AT&T Park are his snot rockets. Six, seven, 20, even 30 times a game, Bumgarner gives himself a big, ol' fashioned nose blow. One dedicated Giants fan keeps track of the snot rockets-per-game statistic. There are GIFs and Twitter accounts (@snotrockets40) and T-shirts that celebrate the lefty's peculiarities on the mound.

Bumgarner takes it all in stride. For now, he's focused on getting ready to lead the Giants on Opening Day. "It's a huge honor and a blessing, especially with the other guys here," he said, referring to rotation-mates Matt Cain, Tim Hudson, Tim Lincecum and Ryan Vogelsong. "I'm thankful for it. It's a cool box to check off on your list of accomplishments."

Will he be nervous? Maybe just a bit, he allowed, but Bumgarner has plenty of experience tuning out the excitement and jitters that come along with pitching in a big game. He's pitched in seven postseason games for the Giants, on their way to two World Series championships in the last four years. In 2010, he became the fourth-youngest pitcher in baseball history to win a World Series game, when he started Game 4 of the series against the Texas Rangers, on the road, and pitched eight innings of three-hit ball. The next night, the Giants won their first World Series since moving to San Francisco.

He's ready to shine on the big stage again. "Halfway through last season, I locked in with my mechanics," he told me. "It's the best I have ever felt. I'm where I need to be."

* * *

Wendy Thurm is a contributing writer at FanGraphs and Bay Area Sports Guy. She has also written for ESPN.com, SBNation, The Score and the Wall Street Journal. You can follow her on Twitter @hangingsliders.