ST. LOUIS -- The Cardinals' decision to option left-hander Marc Rzepczynski to Triple-A on Monday wasn't so much meant as a wakeup call to a struggling bullpen, general manager John Mozeliak said, but as a challenge specifically directed at Rzepczynski. The move wasn't solely dictated by results, either.

Rzepczynski learned of the reassignment after Sunday's game, one in which he allowed two earned runs and another two inherited runners to score in one-third of an inning. That only further swelled his negative season numbers. He allowed six of seven inherited runners to score in his eight relief innings. That's in addition to the seven runs and 13 hits he's allowed.

"I felt like it just wasn't getting done," said Mozeliak, whose corresponding move was to add right-hander Seth Maness to the big league roster. "He needs to go down to Memphis, work on a few things. Obviously, working ahead and in pitchers' counts should benefit him. … I get there are some other people not performing well, and people are asking me about them as well. I just don't want to make wholesale changes just to do it. But I do think everybody realizes we have to make some changes."

Indeed, the Cardinals seemingly had other candidates for a demotion, as four others also enter Monday with ERAs higher than 4.00. The bullpen's ERA sits at a Major League-worst 6.08 after allowing another 11 earned runs over the weekend.

The decision to unplug Rzepczynski, though, was more than just numbers-based. It was a pointed message by the club's decision-makers, who perceived a lack of desire from him this year.

"When you drill down more specifically, it's seeing some of that competitiveness and fire, and I just wasn't really seeing that drive this year," Mozeliak said. "I noticed it early in spring, and it sort of just carried over. … You're coming in with opportunities to do things, and it just wasn't getting done. When you think about inherited runners scoring, he was just becoming ineffective. We can't just keep rolling it over and over again, thinking we were going to get a different outcome. I think they define that as insanity if we keep trying it that way."

This trip to the Minors is the first for Rzepczynski since 2010, when he was with the Blue Jays. The Cardinals acquired him in a midseason trade the following summer, and the lefty proved to be a critical piece in the bullpen of an eventual World Series championship club.

He was decent in 2012, too, though his ERA never really recovered from a tumultuous six-week period in May and June. Yet from July 1 through the end of the season, he posted a 1.83 ERA.

That late-season surge and the belief that Rzepczynski would be better than his cumulative numbers last year prompted the Cardinals to sign him to a $1.1 million contract in his first offseason of arbitration-eligibility. But after opening 2013 with three scoreless appearances, he had been scored upon in four of his last six.

"He was very much in agreement that there were a couple things off that he's having trouble finding right now," said manager Mike Matheny.

Rzepczynski will be plugged into the bullpen at Triple-A, where, Mozeliak said, it'll be a priority for him to get regular work. When he pitches, it will likely be for full-inning stints, not simply in lefty-on-lefty situations.

His departure marks the first move the Cardinals have made this month to address their beleaguered bullpen.

When the Cards were doing their offseason planning, they envisioned a late-inning sequence of Jason Motte, Mitchell Boggs and Edward Mujica.

"Obviously, that lineup is no longer holding true," Mozeliak said. "We're making adjustments, and hopefully, we can find the right combination."