Dodgers trainer Stan Conte wonders, too.
"I wish I could answer that," Conte said of the left-hander, whose Taiwanese name has become synonymous with another left-hander, Tommy John. "There's not a good medical reason why, all of a sudden, he feels so well and is pitching so well."
Ever since his elbow unraveled in his first professional start 10 years ago, leading to the first of two Tommy John surgeries and four operations, total, Kuo's career has been one comeback after another.
And every time he's taken the mound, the organization has held its collective breath.
"Everybody assumed it was just a matter of time before he blew again," said A.J. Ellis, who has caught Kuo at various levels since 2005.
But after being treated with kid gloves in preceding years, Kuo is now sometimes pitching on back-to-back days, is able to pitch longer than one inning, has been elevated to closer and, as the Dodgers open a series in Milwaukee on Tuesday night, is almost being treated like...
"Like he's no longer an injured guy," said Acey Kohrogi, the Dodgers director of Asian operations, who was instrumental, along with then-director of international operations and current Seattle general manager Jack Zduriencik, in signing Kuo as a 17-year-old for a $1.25 million bonus in 1999.
Kuo's stats this year are astounding: a 1.40 ERA, 54 strikeouts in 45 innings, a .146 opposing batting average (.096 at home, .098 vs. left-handers) and an All-Star appearance. His fastball touches 96 mph, and he hides the ball in his delivery, so batters have trouble picking it up.
But as recently as April, Kuo was on the disabled list after being scratched from a goodwill start in his home country because of that elbow.
"When he had the problem before we went to Taiwan, I really felt this was the beginning of the end," said Conte. "And I've thought that every year I've been here, since '07."
Ballplayers are quick to get labeled, but you don't hear many tagged with the word Conte uses for Kuo.
"He's an outlier," Conte said, because Kuo's recovery defies conventional medical wisdom.
His story is a life lesson in resilience. He was put on the 40-man roster in 2002 by then-general manager Dan Evans after pitching only 36 1/3 innings over three seasons, missed the entire 2003 season due to his second Tommy John operation, was taken off the 40-man roster in 2004 after having pitched a total of 42 1/3 innings in five years, but fought his way back and finally reached the Major Leagues in 2005.
His daily therapy regimen is legendary among any who've witnessed it, starting at 12:30 p.m. for a 7:10 night game.
"I wish you guys could see what he puts himself through," said Conte. "He's in constant motion until 11 at night -- ice, heat, ultrasound, message, stretch, flex, leg work, working all the time just to pitch an inning."
And as if the operations weren't enough of a handicap, Kuo also fell victim last year to the yips, an inexplicable loss of fine motor skills. In pitching terms, he not only couldn't throw a strike, but warming up to come into a game early last season, Kuo couldn't throw a catchable pitch to Brad Ausmus, two of them sailing over the bullpen gate and stopping play.
"I never thought he'd pitch again," said Ausmus. "From my experience, you don't see people come back from that issue. I felt terribly for him. I'm happy I was proven wrong."
Kuo spent two months on the disabled list and beat the yips, which disappeared as mysteriously as they surfaced.
"Maybe it was pressure. Maybe I wasn't healthy. I don't know," said Kuo. "That problem I don't have to worry about anymore. A lot of people have helped me, especially the trainers and doctors. And Joe [Torre] has been good to me."
And, except when he considered retirement in 2003 upon receiving the discouraging news that he again needed Tommy John surgery, Kuo has retained his smile and quick wit.
"I'm not the only guy with problems," Kuo said. "Maybe I'm the only one with four surgeries, but everybody has issues. I'm not special. I've got a good life. I'm a Major League player; I make some money. I'm happy with what I am."
What Kuo has been is off the charts, from the time Kohrogi first saw him blowing away adults as a teenager, to his pro debut, when he struck out seven of 10 batters and blew out the elbow and one of his many returns in front of then-general manager Evans, who saw Kuo strike out 13 in five innings on the back fields in Vero Beach.
"[He was] absolutely dominant, I'll never forget it," said Evans, now an agent. "It sticks with you. He was special. Everything we did with him, it was with that game in mind. Others had heard the hype. I knew it wasn't hype; it was the real deal. You see his dominance now. You should have seen him then. He'd throw 96-100 miles per hour, as unhittable as I've seen my entire career -- explosive, lively, rhythmic. No-chance stuff. Great pick by Zduriencik. Figured he'd be a No. 1 or No. 2 [pick] at an early age. John Boles called him a once-in-a-lifetime arm."
While Kuo was healing from his second Tommy John procedure in 2003, Evans had him travel with the Major League club to chart pitches, soak in the atmosphere and learn a strong work ethic from Darren Dreifort, another two-time veteran of Tommy John surgery.
"A lot of people thought he'd never come back," said Evans, "but it was a simple decision for me."
Kuo has survived like a cockroach (Conte's term again). Since Kuo signed, the Dodgers have had two owners, five general managers and four field managers. No player has been in the organization as long.
Ned Colletti inherited Kuo from Paul DePodesta and has benefited more than any of Kuo's other general managers, not that sticking with Kuo was always a no-brainer.
"The kid deserves a lot of credit for perseverance," said Colletti. "He refused to give up or give in. He goes to the All-Star Game. How many relievers go and aren't closers? His personality, his work ethic, his talent allow you to have patience. He's not somebody that gives up easily on himself, so it wouldn't be right for us to give up easily on him."
Ken Gurnick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.