The former Dodgers pitcher, who signed with Seattle in the offseason, was one of the league's most dominant lefty relievers in 2010. A year later he was suffering through his worst statistical season -- one featuring a stint on the DL with an anxiety disorder, and culminating with October elbow surgery, the fifth of his career.
In his mind, there's only one thing to focus on in order to avoid another year like 2011, where each time he stepped to the mound, it seemed as though his control worsened.
"I just need to get that confidence," Kuo said following Saturday's workout at Peoria Sports Complex. "Be on the mound, and don't be afraid about anything. Try to stay healthy and get stronger. I'll do whatever I have to do."
Kuo's psychological struggles kept him away from the strike zone and eventually landed him on the disabled list last May. When he returned he never seemed himself, eventually finishing the 2011 season with a 9.00 ERA and 23 walks in 27 innings.
Kuo clarified that his confidence will come, so long as his elbow doesn't falter.
"If I stay healthy, I'll be able to do whatever I want to do," said Kuo, adding he has felt great in camp thus far after arthroscopic surgery Oct. 28. "I'll be able to get my confidence back and really be able to show people what I can do."
What he can do is post a 1.20 ERA in 60 innings with a WHIP below 0.8. What he can do is strike out 11 batters per nine innings, while holding opposing hitters to a .139 batting average.
If Kuo can put up anything close to those 2010 numbers, Mariners pitching coach Carl Willis says he'll make a huge impact in the Seattle bullpen. Willis sees Kuo not just as a lefty specialist, but potentially someone who could anchor the seventh or eighth inning for manager Eric Wedge.
But to Willis, the key is to let Kuo progress at his own rate, without rushing him into a situation he isn't yet ready for. By doing so, Kuo's confidence should rise and he'll be able to showcase his talent without the anxiety troubles.
"I've seen a guy that throws strikes in Spring Training in the bullpen," Willis said. "I think that's huge because he needs to take that confidence he has in those bullpens out into games and pound the strike zone, because his stuff is not a question."
Kuo says he has been greeted with open arms in the Mariners clubhouse -- a welcome change of scenery for the 30-year-old, though it was no doubt tough for him to leave the organization he signed with in 1999 as an amateur free agent.
He made his first appearance for Seattle in a game-like situation during Friday's intrasquad scrimmage, where he walked two batters and retired the other three he faced in his lone inning. Kuo is not slated to throw in Sunday's intrasquad game, but he will throw a side session.
"It's been a while since I got surgery, so it's good to get out there and face hitters," Kuo said. "I walked a couple guys, but I've been working hard."
Willis had no problems with what he saw from Kuo on Friday, adding the coaches' expectations for Kuo can't be too high this early because of the recent surgery and recovery following his shaky 2011 campaign.
"Because he had a down year, we need to make sure we temper the expectations early, and allow him to go out and compete," Willis said. "Then he'll show us what he can be."
Wedge described Kuo as "a veteran guy, who knows what his role is," and said, he, too, has been impressed in camp. But as for Kuo's long-term role with the club, Wedge won't know until Kuo lets him know.
"He'll define it," Wedge said.
In doing so, Kuo may also be defining the Mariners' bullpen in 2012.
AJ Cassavell is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.