Kirk Clark is a man on a mission.

Signed as a free agent by the Houston Astros last August after going undrafted following his junior season at Creighton, the Moline native is showing opponents what they missed.

Pitching for the Astros' low-A farm club, Lexington, the 6-foot-2 right-hander shares the lead in the South Atlantic League with 18 saves.

"Through high school and junior college and at Creighton, I heard every year that I was going to get drafted, and it never happened,'' Clark said. "I'm here trying to cause a little havoc and let everybody know that they made a mistake."

So far, so good.

Clark went 2-1 with a 1.89 ERA in 10 late-season relief appearances last season for short-season Tri-City in the New York-Penn League.

He was assigned to the Lexington roster to open his first full season as a professional, and it didn't take him long to find himself in a closer's role for the first time in his career.

"That's been a little surprising," he said. "I came out of spring training as a long-inning relief guy who might occasionally be a set-up guy in some situations. A couple of weeks into the season, I found myself closing games. It was something I didn't expect."

Clark dabbled as a closer in an Alaskan summer league, where the Astros first saw him, and in a handful of early-season games in 2009 at Creighton.

"I was never a full-time closer who could be brought in almost on a daily basis, though, not until now," Clark said. "It's been different. When you're called on now, you have to be ready."

A pitcher who relies heavily on his fastball and changeup, Clark is 3-1 with a 4.08 ERA in 33 relief appearances for Lexington. He has struck out 37 batters and walked 17 in 351/3 innings.

He's working to develop consistency in his slider and is making progress.

Legends pitching coach Ricardo Aponte was the Washington Nationals bullpen coach in 2006, and Clark said he is learning on a daily basis from him.

"He knows what he is talking about. For me, there are good days and bad, and I know it's consistency in everything I do that is going to lead me to the next level," Clark said. "I work toward that every day. Playing pro ball is what I want to do."

Clark, who spent the offseason working out at Quad-City Sports Performance, has adjusted to the long bus trips that are frequent in the South Atlantic League.

"It's a change, but it's part of the deal in A ball, and you put up with it and get ready for another game," Clark said. "I love what I'm doing, and the more I play, the more I want to make this last as long as it can."