General manager John Mozeliak said the Cardinals would go with 13 pitchers for at least the next few days and would demote a position player before beginning a three-game series against the New York Mets on Tuesday. St. Louis relievers have averaged more than four innings the first 13 games.
"I don't look at it as a Band-Aid at all," Mozeliak said. "We're looking to add depth to an area that needed it."
Mozeliak said he wasn't sure how long the Cardinals would need an extra pitcher, which will leave them with only four bench players. The most likely cut is rookie third baseman David Freese, batting .158 in 19 at-bats while losing time to Brian Barden and Joe Thurston.
Boyer was 0-1 with a 40.50 ERA in three games, allowing six runs in 1 1/3 innings. He appeared in a career-high 76 games last year with Atlanta while also setting highs in innings (72) and strikeouts (67).
"Our scouting reports were very positive," Mozeliak said. "We just thought it had an awful lot of upside for us."
The Cardinals acquired the 26-year-old Barton in the Rule 5 Draft in 2007. He batted .268 with two home runs and 13 RBIs last year as a rookie and was hitting .107 with one RBI at Triple-A Memphis.
Barton had little chance of contributing in 2009 due to the Cardinals' crowded outfield.
"He had a pretty good year for us last year but the reality is our offense is stacked up right now it just is going to be tough for him to get major league at-bats," Mozeliak said. "In fairness to him, this is a better opportunity."