Knuckleballer Charlie Zink, who spent eight years in the Red Sox organization, agreed to a minor-league deal with the St. Louis Cardinals. The 30-year-old went 63-60 with a 4.25 ERA during his Sox minor-league career, and spent parts of the last five years in Triple A Pawtucket.

He was named the International League Pitcher of the Year in 2008, when he went 14-6 with a 2.84 ERA. That same year, Zink made his lone appearance in the majors for the Sox, allowing eight runs in 4.1 innings in a no-decision.

According to Zink’s agent, Jim Masteralexis, Zink received an invite to major-league camp with the Cardinals. He is expected to compete for the team’s Triple A rotation in Memphis, but the fact that the Cardinals do not currently have a fifth starter also played into the pitcher’s determination that St. Louis offered a good opportunity. The Sox did not offer Zink the opportunity to return to the organization, nor did the right-hander seek one.

“We are grateful to the Red Sox for having the patience with Charlie to learn and refine the knuckleball, but it is time to move on,” Masteralexis wrote in an email. “Charlie is excited about this opportunity. It is a great organization, has a great major league pitching coach in Dave Duncan and it is a fresh start. … Charlie needs a fresh start and opportunity.”

In some respects, Zink’s departure is a commentary on the changing shape of the Red Sox’ minor league system over time. When he signed with the Sox as a undrafted free agent on the recommendation of college pitching coach (at Savannah College of Art and Design) Luis Tiant, the Sox had few useful pitchers in the system who could help the major-league team. But over time, Zink saw the organization become flush with talented young arms. Last spring, he reflected on his time with the Sarasota Sox in 2004 and the Portland Sea Dogs in 2005, when he was suddenly flanked by a staff that consisted of Jon Lester, Jonathan Papelbon, Manny Delcarmen and others.

“You could see at that time there was a good group of prospects coming up. They were serious prospects. They were going to be impact players. That was the first time I ever noticed it. Before that, there wasn’t a whole lot here. Then it got big real quick, and all of a sudden we had draft class after draft class filled with power arms who were smart,” Zink said. “It’s not frustrating, but you see it. They just keep grooming younger and younger guys with power arms. You see them come and come, and keep going up.”