The team made a formal announcement at an afternoon press conference at Minute Maid Park.
"I felt it was time for a change," McLane said. "Our goals, our objective is to be a champion. I just feel we need a fresh start."
McLane said he met with Purpura following the Astros' 5-4 win over the Pirates on Sunday and informed him of his decision. Monday morning, McLane called Garner and dismissed him as well.
"[Purpura] was disappointed," McLane said. "He certainly wanted to continue, but I felt, for a number of reasons, we needed a new direction, a new configuration. To play with more enthusiasm and to be a champion."
Purpura declined in an e-mail to make any public statements. Garner took the news well, expressing gratitude toward the organization for hiring him in 2004 and giving him a chance to win.
Losing clearly was unacceptable to McLane, who's watched a fair share of often humiliating defeats from his Diamond Club seat right behind home plate. It's difficult to decipher which was the final straw, but the owner did mention several incidents that may have led to his ultimate decision.
McLane made references to the obvious elements, such as the club's poor record this year and the Jason Jennings trade, which clearly did not work in the Astros' favor. But McLane also alluded to the Draft, the player-development system and even Hunter Pence's injury, which was caused by a flawed sliding technique and wasn't corrected during his time in the Minor League system.
"It's a series of things," McLane said. "Being a general manager, the Major League team is the thing that's most obvious. But we have 41 full-time scouts out there and we have player development. It takes a lot of leadership. I talked a lot the last year and this year that I've been disappointed. And I'm disappointed that we have not done better in this homestand."
The Astros were 2-5 against the Nationals and the Pirates to begin the current 10-game homestand. Losing to two sub-.500 teams in a ballpark filled with many empty seats didn't sit well with the owner and surely contributed to his decision.
McLane often roams the stands and converses with fans, who have expressed plenty of dissatisfaction throughout the season. McLane, one of the most sensitive owners in the business in terms of public perception, did not turn a deaf ear to the ticket-buying fanbase.
"This was two years in the process," McLane said. "I've observed things, watched things, talked to literally hundreds of people as I go through. I went through the stands yesterday, and every game. I ask people, 'What do you think?' It's amazing what people will tell you. It's the impact others had on me, over a period of time."
During Jeff Bagwell's uniform retirement ceremony on Sunday, Purpura was roundly booed by the crowd when he was introduced. Did that contribute to McLane's decision?
"I had already made up my mind [to dismiss him]," McLane said. "No one has worked harder for the Houston franchise than Tim Purpura. He's been here 14 years. When you're in charge of player development, you're gone about 80 percent of the time and you're all over the world. Tim worked hard. In the general manager's job, he's worked at it intensely. I was disappointed for Tim and his family. But we have to accept this is a tough game. Winning is what it's about. We had to recognize that."
Smith, the club's president of baseball operations, will serve as GM only until the end of the season, at which time the Astros hope they'll have a permanent GM in place.
Cooper will use the final 31 games as an audition. The Astros will conduct an expansive managerial search when the season ends, and Cooper will be a top candidate to earn a permanent role.
That partly answers the question on everyone's minds Monday: Why now?
"I wanted to get to know Cecil Cooper better, and this is an opportunity for Cecil to show us his leadership," McLane said. "If we made this decision after the season was over and said, 'Well, how's Cecil going to be as manager?' We have 31 more important games. We want to continue to move up."
Garner ends his managerial tenure in Houston with a .524 winning percentage and two postseason appearances. Purpura spent 14 years with the Astros organization, the last three as GM. Prior to that, he was assistant general manager and the director of player development.
"Tim and Gar are good people," Smith said. "They worked hard, they cared very much about the Houston Astros, they care very much about baseball. But as we all recognize, this is a performance-driven industry, results oriented. The record speaks for itself."
And the Astros' record is 58-73, good for fifth place in the NL Central. They're a fraction of a percentage point out of last place.
The Astros will use the last month of the season to evaluate everyone -- Cooper, the coaches and the players, especially the young prospects, some who are already with the Astros and a few who will arrive on Sept. 1, when rosters expand to 40.
"We'll use that time to take a look at young talent in the organization, to prepare for the 2008 season," Smith said. "That's not to say that we're giving up where we are. We don't want to finish last, we don't want to finish next to last. Hopefully, we can make a surge and finish up on a more positive note.
"It's a very important time for the organization from the standpoint of its image, from the standpoint of the young players that we'll be looking forward to in the future to contribute."
Cooper, 57, was the team's bench coach for the past three seasons. He previously served as the bench coach for Milwaukee in 2002 and spent both 2003 and 2004 as the manager of the Triple-A Indianapolis club in the Brewers organization.
Smith, currently Houston's president of baseball operations, is a former Astros GM. The 2007 season is his 50th in the game of baseball. He started his career in the Reds farm department in 1958 and came to Houston in 1960, when he was named assistant to the general manager Gabe Paul for the new National League expansion franchise that would become the Colt .45s.
"There is no one in America that has more experience in leadership and player development and helping develop a successful organization," McLane said, referring to Smith. "He and I will get involved starting tomorrow in trying to do a search, the search that the Commissioner outlined a couple of years ago. Hopefully, by end of the season, we'll have a general manager."
Alyson Footer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.