MESA, Ariz. -- When Corey Koskie first suffered a concussion in 2006, he was abruptly forced out of the game he loved and spent 2 1/2 years in what he called his "personal jail." On Saturday, the third baseman walked away from baseball on his terms, saying it wasn't worth the risk.

"This is what I love to do -- I love being out there, being with the guys, the whole competition," he said. "There's no way you can replace it. But at some point you have to look at it realistically and say, 'Is it really worth sacrificing the rest of your life for a game?'"

It's been an emotional week for Koskie, who spent last Sunday night in an Arizona hospital with his 6-year-old son Joshua, who suffered a concussion playing football with his brother.

The doctors initially wanted to send Joshua home, but Koskie stepped in. They'd given the family a piece of paper with symptoms to look for, and Koskie felt it wasn't informative enough. Koskie knows concussions are difficult to treat. He went more than two years before finding someone who could help him.

"The last 2 1/2 years, I've been dealing with a lot of people with concussions," Koskie said. "I've been dealing with parents trying to send their kids back out to play with concussions as soon as they get better. I wanted to get back out there and I wanted to play. Is it worth it? Is it worth the risk to go out there and play a couple more years vs. having the rest of my life, living a normal life?

"I know I could go out there and do it. But is it worth the risk to go out there and find out?"

On Tuesday in Glendale, Ariz., Koskie started at third for the Cubs against the Los Angeles Dodgers. At one point in his three innings on the field, he dove for a ball, then got to his feet and started doing a mental checklist to make sure he was OK.

He felt a little "funky." Was it the heat? Was it his head?

"One thing I do know is after the play, I was sitting in the clubhouse saying, 'What am I doing here?'" he said.

Koskie originally suffered the concussion trying to catch a popup July 5, 2006, playing for the Brewers at Miller Park. Cincinnati's Felipe Lopez lofted the ball to shallow left, and Koskie went after it. He reached back awkwardly for the ball, lost his balance and fell. His head didn't hit the turf, but he did suffer a concussion.

Bill Hall was playing shortstop for Milwaukee that day.

"When you look at the play, it didn't look that harmful," Hall said. "Nobody screamed, nobody cringed. For something like that to end your career, that's pretty unfortunate.

"I'm obviously sad. But he had his family to think about, his kids, and I'm sure he wanted to be functional for them for the rest of his life. We all felt for him [during his comeback], because you knew he still had it in him to play baseball."

Koskie didn't feel symptom-free until 2 1/2 months ago, and was cleared to play for Team Canada but never got into a World Baseball Classic game. He signed a Minor League contract with the Cubs on Feb. 28, and went through three days of physicals. He credited team physician Dr. Stephen Adams, athletic trainer Mark O'Neal and general manager Jim Hendry with helping him make this decision.

"One thing I can honestly say is these guys here ... they care about you as a person," Koskie said of the Cubs staff. "Everybody saw I still had some stuff left in the tank, but they looked me in the eye and said, 'Is this really what you should be doing?'"

Koskie realizes he could help the Cubs, who were looking for a backup third baseman. But his life is worth much more.

"There's going to be a first collision, a first dive," he said. "After playing, I don't want to be analyzing it."

He was a career .275 hitter in nine seasons with Minnesota (1998-2004), Toronto (2005) and Milwaukee (2006). A left-handed hitter, he primarily played third base and his .966 fielding percentage ranked sixth among all Major League third basemen from 1998-2006.

In 1999, Koskie batted a career-high .310 with 21 doubles, 11 home runs and 58 RBIs in 117 games for the Twins. In 2001, he set career highs with 26 home runs, 100 runs scored and 103 RBIs with Minnesota. He helped lead the Twins to three consecutive postseason appearances from 2002-04.

Koskie said he can leave the game now with a better feeling than he did after the initial injury. In the last 2 1/2 years, he was in what he called his "personal jail," being unable to play with his children, unable to drive, unable to eat in a restaurant. One doctor had suggested wearing ear plugs to eliminate distractions. That's not how he wants to spend the rest of his life.

"Look at the facts -- I'm 35," he said. "I spent the last 2 1/2 years [struggling]. I still can play. But on the other side of it, if I play I want to be able to play 100 percent. I don't want to be thinking, 'What if I do this? What if I dive?' It might be a little different if I was 23, I didn't have any kids, I didn't have any family, I didn't have a wife.

"What am I trying to do to squeeze out for two more years? I've always said my goal was that I wanted to be able to play baseball again. I knew that if I was able to play baseball again, I was over it, I would be able to live my life. I got to that goal. You get there, and you want a little more. So I thought, maybe I'll play for Team Canada."

Some other teams became interested. Then he got the call from the Cubs. All he wanted was a chance.

"You get caught up in the whole, 'It'd be great if I come back -- it'd be a great story,'" Koskie said. "The bigger story that really needs to get put across is that I had my opportunity to play, I still could play, but is it really worth it to play?"

He will head home now to spend time with his family. Maybe he'll consider coaching in the future. His son, Joshua, is fine. So is Koskie.