GLENDALE, Ariz. -- You could run through a lot of adjectives to describe Kenley Jansen before you landed on "mean."
He's the Los Angeles Dodgers' gentle giant, a hulking, laid-back kid, blessed with a big right arm and a natural feel for pitching. He's also lucky. Had he lived 30 years earlier, his career might have come screeching to a standstill just when it was ramping up because of an irregular heartbeat.
But two minutes of conversation will tell you that angry isn't his usual mood. It's so hard for Jansen to get mad, in fact, he's been forcing himself to all spring.
And with his size (6-foot-5, 260 pounds) and his arm, you wouldn't like him when he's angry.
"Those guys are trying to take your bread, they're trying to take your job," Jansen said. "I want to go out there mentally like, 'I don't care about you. I'm going to get you down. I'm going to win this battle.' I'm trying to build that angriness in my body. I know it's hard to sometimes, but I'm trying."
It's all about mastering the mindset while learning the craft.
He remembers the date off the top of his head: July 31, 2009. He remembers the opponent: Lancaster. He remembers the result: 10 pitches, nine strikes, two strikeouts and an easy stroll back to the dugout.
That was the day Jansen made his professional debut as a pitcher after four minor-league seasons as a light-hitting catcher.
"I fell in love with it," Jansen said. "I know that's my thing I do the best."
And, just when it started to click, they almost had to tell him he couldn't do it any longer.
In July 2011, with the Colorado Rockies in town to play the Dodgers, Jansen started feeling odd. He was tired, but anxious. His palms were sweaty. He told a trainer, who felt his pulse and had him taken to the hospital.
Doctors found that his heart was racing up to 200 beats per minute in an irregular pattern triggered by a condition known as atrial fibrillation. Its cause is a mystery, but atrial fibrillation -- or AFib -- derives from extra electrical impulses originating in the pulmonary veins. It usually happens in patients 70 years old and up, but is rare in otherwise healthy 20-somethings.
Doctors put him on blood thinners to reduce the risk of stroke, and got his heart back into its proper rhythm.
A little over a year later, with the Dodgers in Colorado, it came back. Jansen spent the next three weeks on the disabled list. Both times, Jansen's heart failed to return to its normal rhythm on its own, forcing doctors to shock it back into sinus rhythm.
His cardiologist recommended he undergo a procedure known as a catheter ablation. Jansen was ready to put the condition behind him. In October, he was anesthetized for three hours while a doctor threaded small, flexible tubes from veins in his groin to his heart, where he zapped the heart tissue that was triggering the irregular beats. Jansen spent two months in Los Angeles recovering, then a month in his native Curacao, and now he's under no restrictions in camp with the Dodgers.
"My heart is finally in the right place now," Jansen said.
The Dodgers think they're seeing fast results.
"He looks better and seems more energetic than we've seen him in a long time," Dodgers manager Don Mattingly said.
Jansen's talent, though raw, is almost limitless. Over the past three seasons, hitters have batted .148 off him, the lowest in the majors since 2010. They have missed on nearly 36 percent of their swings off him, the third-best rate in the majors. He averages 14.58 strikeouts per nine innings, second best all-time among pitchers with at least 125 career innings.
Some observers find it baffling that the Dodgers are giving Brandon League the first crack at their closing job, but eventually the pitcher performing better figures to be finishing games. Jansen said he doesn't mind. At 25, he's in no hurry to be a closer, though he says he knows he can do it.
Besides, he knows he's raw. So raw, the San Diego Padres' Evereth Cabrera scored the go-ahead run off him last year by stealing home. He struggles to keep runners from advancing at will. He already has been called for a balk this spring.
Imagine how good he might be if he can tighten up aspects of the game that don't involve absolutely dominating hitters. Mental acumen shouldn't be a problem. He speaks four languages fluently. In Curacao, his family spoke the native language of Papiamentu. In school, he learned Dutch, Spanish and English.
The other day, Jansen was working on the Camelback Ranch mounds with assistant pitching coach Ken Howell. They were doing a drill intended to align Jansen's body in the proper direction, to get his body and arm flying directly toward home plate. It was all about understanding lines and angles.
Jansen started getting frustrated, having battled bad habits each of the past three seasons.
"Well, let me ask you this: 'How long you been doing this?'" Howell asked. "Have you ever given up five runs in a game yet? No? You haven't been pitching long."
There's a first time for everything. So far, there haven't been many experiences Jansen couldn't bounce back from.