HOUSTON — Tony DeFrancesco helped Houston's Triple-A affiliate find success.

The Astros hope he can do the same for their young, struggling major league club.

DeFrancesco was chosen interim manager Sunday, a day after Brad Mills was fired.

"There's going to be a commitment to excellence,'' DeFrancesco said. "Believe me, I want to be the guy that changes the environment around here. I grew up a winner, I had success in the minor leagues, and it's time for it to translate to the major league level. I'm sure I'm going to make mistakes, but that's part of baseball.''

DeFrancesco managed Oklahoma City to a 67-60 record and has the RedHawks contending for a playoff spot this season. Houston has the worst record in the major leagues at 39-83.

He takes over an Astros club that is the youngest in the National League at 26.5 years - and even younger than the Oklahoma City team, 27.3 years.

In his third season running the Astros, Mills was dismissed Saturday night after Houston lost to the Diamondbacks 12-4.

Hitting coach Mike Barnett and first base coach Bobby Meacham were let go along with Mills. Dan Radison will take over in the interim as first base coach and Ty Van Burkleo will be the hitting coach.

General manager Jeff Luhnow said he made the decision not to bring Mills back for next season about a week ago.

"Once that decision was made, it made a lot of sense to make these decisions sooner rather than later,'' Luhnow said. "We didn't want to have a lame-duck administration and wanted to get some new blood in here.''

He told Mills after the game Saturday night that he was being let go in what was about an hour-long meeting.

"I have a great deal of respect for Brad, and he's a great baseball manager,'' Luhnow said. "He'll have a long career moving forward. To a certain extent, I sensed some relief, but I'm not going to speak for him. It's been tough.''

Luhnow called DeFrancesco a winner, and the new manager is looking forward to improving this team.

"We want a staff that is able to work with young players who are on their way up and get them better,'' Luhnow said.

Morale has sagged for the Astros as they've gone into a tailspin during the summer after trading several high-priced veterans mostly for prospects. They have slashed almost $40 million from their opening-day roster and have a remaining payroll of just $21.3 million.

Francisco Cordero and Jed Lowrie, two of Houston's three highest-paid players, are on the disabled list. That leaves Ben Francisco as the only active player making more than $750,000.

Luhnow traded Carlos Lee to Miami on July 4 as the Astros went all in on their rebuilding effort under new owner Jim Crane. They have gone 7-32 since that deal, including a franchise-worst 12-game losing streak.

Lee, however, was only the first piece to be jettisoned. After that, Houston got rid of pitchers J.A. Happ, Brandon Lyon, David Carpenter, Brett Myers and Wandy Rodriguez before wrapping up a busy month by sending third baseman Chris Johnson to Arizona.

Luhnow said he needed to do something to shake things up.

"We made three changes because we really wanted to change the mix and bring in a new environment,'' he said. "We want to have success here and that starts with making the players excited to be here.''

Mills was the first big league manager to be fired this season. He was 76-86 in his first season with Houston and a franchise-worst 56-106 last year. He took over for Cecil Cooper, who was also fired during the season, as was his predecessor Phil Garner.

Luhnow said he'll begin the search for a new manager immediately.

"Our goal is to assemble the best possible staff to fit the Houston Astros organization,'' he said. "We're going to be working diligently on the search for the remainder of the season or into the offseason, however long it takes. We have no timetable.''

Luhnow knows that things won't change overnight, but he's hoping this is the start of something positive for Astros.

"What we want to accomplish for the rest of the season is to win as many games as possible and put ourselves in a position where we have the best staff and group of players as we can possibly have,'' Luhnow said.

The players feel bad that they weren't able to play well enough for Mills to keep his job.

Reliever Wesley Wright, who is the longest tenured member of this exceedingly young team, said it was sad to see Mills go.

"I think it's all on us. No matter who is the manager, it's up to us to make plays,'' Wright said. "We're pretty much responsible for wins and losses, for the most part. It just boils down to what we do on the field. The manager can bring what he can bring, but at the end of the day, it's on the players.''

The 49-year-old DeFrancesco has been a manager in the minor leagues for 17 seasons and managed Oklahoma City since 2011. He was the manager of Triple-A Sacramento for seven seasons before joining Oklahoma City where he won one Triple-A championship, three Pacific Coast League championships and six PCL Southern Division titles.

His only major league coaching experience came when he was Oakland's third base coach in 2008. DeFrancesco played for nine seasons in the minors and appeared in 567 games, but never advanced past Triple-A.

Infielder Brett Wallace and a number of Astros are very familiar with DeFrancesco after playing for him in Oklahoma City this season.

"He's passionate, he wants to win, and he's definitely a good motivator,'' Wallace said. "He's always won, and he's passionate for the game. He'll want to make us the best we can be.''

The Astros selected Tom Lawless as their Triple-A manager after Sunday's game. He had been working as Houston's minor league roving infield instructor.