The Pirates made the move after Morris' start on Saturday night against the Phillies when he lasted only 1 2/3 frames. He was tagged for six runs (three earned) and six hits.
"It's incredibly difficult," Pirates general manager Neal Huntington said. "Matt is the true professional; Matt is on and off the field everything that we want our guys to be. He's a gamer, he's a warrior, he competes every pitch he throws has a purpose. He wants to be successful and he's worked as hard as he can to be successful.
"Mother Nature has taken its toll on him right now, and as we talked about the various options going forward, we kind of came to the mutual decision that it was best for Matt to go in a different direction and us an organization to go in a different direction."
Morris plans to return to his home in Jupiter, Fla., and indicated that his career is over.
"Once you mentally turn it off, it's hard to turn it back on," Morris said. "When you lose your edge competing and the confidence is down, it would be hard to pitch again."
Morris pitched for 11 years in the Majors, with stops in St. Louis, San Francisco and Pittsburgh. A two-time National League All-Star, he has a career record of 121-92 with a 3.98 ERA.
"I'm proud of my career," Morris said. "I didn't mean or want for it to end this way, but I always said the other team will let you know when you're done, and with the outings I've had, some of the fan appreciation has not been so great. But it's all part of it and it's time to move on."
The Pirates recalled right-hander John Van Benschoten from Triple-A Indianapolis to replace Morris on the roster. Van Benschoten was 4-0 with a 1.88 ERA. He will work out of the bullpen in long relief.
Lefty Phil Dumatrait will take Morris' spot in the rotation. Dumatrait is 0-1 this season with a 4.32 ERA.
The decision to release Morris means the Pirates will eat $11,037,283 in salary, including a $1 million buyout for 2009.
"As an organization, we have to be efficient with every dollar we spend," Huntington said. "Whether it's a dollar in Double-A or it's a dollar on a Major League salary, we have to be efficient and we have to utilize our money. As we looked at the right thing for this team, the right thing for this organization and really the right thing for Matt Morris going forward, we came to the realization that the best thing to do was go in a different direction."
George Von Benko is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.