Runelvys Hernandez will take Chacon's place in the rotation and will make his Astros debut on Friday against the Red Sox. Brian Moehler, Roy Oswalt and Wandy Rodriguez will pitch the upcoming Interleague series with the Rangers that begins Tuesday.
Manager Cecil Cooper pointed to Chacon's inconsistency as the reason for the move. Chacon began the year with nine straight no-decisions and did not allow more than three earned runs in any of his first five outings, but beginning with his start against the Diamondbacks on April 30, the right-hander has turned in a handful of good starts mixed in with some duds.
"That was forgotten," Chacon said, referring to his string of solid outings to start the year. "That's long forgotten."
Chacon was 2-0 with a 4.75 ERA in May, but this month, he's 0-3 with a 9.35 ERA.
"That's basically what we talked about -- more consistency," Cooper said. "I don't want to just blame this on him and say he's the reason why we're playing bad. That's not the reason. If I did that, I'd probably have to point at 25 players plus eight, nine coaches. I'd point the finger at everybody. That's not the case."
Said general manager Ed Wade: "We're not looking to bounce guys out of the rotation, far from it. We want people to succeed in the roles that have been designed for them. Shawn got off to a real good start for us. We didn't get him a lot of runs early and he had a lot of no-decisions, but realistically, we felt over the last several starts that it's been a struggle. We decided to go in a different direction."
Chacon was moved from the rotation to the 'pen while with the Pirates in 2007, not because of poor performance, but because the Bucs bullpen was in desperate need of help. In a relief role, Chacon emerged as a solid setup man and received most of his work in the eighth inning.
Past experience factored into Cooper's decision.
"We didn't say long term, short term," Cooper said. "He's in the 'pen. I would think probably as a late guy, seventh inning on. That's what we talked about. That's what he did last year, primarily. He was pretty doggone good at it."
Cooper indicated this move may not be the only one the club makes. Someone will have to go on Friday to clear a roster space for Hernandez, but more moves may be coming.
"There may be others," Cooper said. "I don't know. We're trying to get better, trying to improve ourselves. If we think there's something that can improve us, we'll consider it."
Wade said there have been no discussions regarding more roster moves.
"There's always a chance, but we haven't talked about it," he said.
Hernandez, 30, is 6-3 with a 3.72 ERA over 15 starts for the Triple-A Round Rock Express this year. He's allowed 35 earned runs over 84 2/3 innings and has allowed 11 home runs. He's issued 23 walks while striking out 63. Opponents are hitting .233 against him.