PHOENIX -- The Arizona Diamondbacks fired Bob Melvin on Thursday, hoping a new manager will be able to get the most out of their talented core of young players.
The Diamondbacks will make A.J. Hinch, their vice president for player development, Melvin's replacement on Friday, according to a person familiar with the move who requested anonymity because the announcement had not been made.
The 34-year-old Hinch is a former major league catcher with no professional managerial experience. His promotion was first reported by radio station KTAR.
The 47-year-old Melvin's firing comes after a disappointing start by the Diamondbacks, who entered Thursday 8½ games behind the Los Angeles Dodgers in the NL West. Melvin, who went 337-340 in four-plus seasons, had one year left on a contract he received after being the 2007 NL Manager of the Year.
"This is a difficult decision, but I feel that our organization needs to move forward with a new voice," general manager Josh Byrnes said in a statement.
Hitting coach Rick Schu also was fired, and pitching coach Bryan Price resigned.
Melvin's stock rose when he guided a youthful but talented group to the NL West title two years ago. He was dismissed because many of the same players have failed to live up to expectations based on that season, when the Diamondbacks posted an NL-best 90-72 record despite being outscored by 20 runs across the season.
Justin Upton, Arizona's 21-year-old right fielder, is off to a solid start, but some of the team's other young players have struggled. Conor Jackson went 1-for-3 in Arizona's 4-3, 10-inning loss at San Diego on Thursday and is batting .191 on the year. Mark Reynolds has struck out 36 times in 102 at-bats.
"We're counting on everybody to develop further," Melvin said in an interview before the season. "We don't rely on one guy to hold up the brunt of this thing. We expect them all to develop and score more runs."
Arizona's few veterans also did little to help Melvin.
Speculation about Melvin's future grew with every 1-2-3 inning by the Diamondbacks' hitters. Arizona entered Thursday with a .225 batting average, by far the worst in baseball.
Team president Derrick Hall, speaking on KTAR on Thursday morning, called the team's play "unacceptable."
Making matters worse for Melvin, the Diamondbacks have been beset by injuries.
Ace Brandon Webb went on the disabled list with a shoulder injury shortly after his opening day start and has yet to return. Then Stephen Drew went on the disabled list with a strained left hamstring. Reliever Tom Gordon, acquired over the winter to shore up the bullpen, is already on his second DL stint.
This is the second time in their 12-year history that the Diamondbacks have changed managers in midseason. In 2004, the Diamondbacks fired Bob Brenly after a 29-50 start and replaced him with Al Pedrique on their way to a franchise-worst 51-111 record.
That disaster paved the way to Melvin's return to Arizona, where he had served as Brenly's bench coach on the 2001 World Series champions.
Melvin's hiring as the Diamondbacks' manager came under bizarre circumstances. The club had selected Wally Backman as manager, but Backman was dismissed four days later following revelations he had been arrested twice and struggled with financial problems.
Arizona then turned to Melvin, who was out after two seasons in Seattle, where he went 156-168.
Melvin made an immediate impact in the desert. He led the 2005 Diamondbacks to a 77-85 record, a 26-win improvement.
Two years later, the Diamondbacks made a surprise run to the NL West title despite scoring 20 fewer runs than they allowed -- a fact that led many to praise Melvin's ability to squeeze the most out of his lineup.
Melvin was honored as the 2007 NL Manager of the Year, and soon after the club extended his contract through 2010.
"I am grateful for all the success and memories associated with Bob," Byrnes said. "Bob has done great things for this organization. Having worked with him for nearly four years, I have a great deal of respect for his character and skills."
Arizona opened its NL West title defense last spring by bolting to a 20-8 record. But after leading the division for most of the season, the Diamondbacks faltered and were caught in the stretch by a Los Angeles Dodgers squad energized by the arrival of slugger Manny Ramirez.
The Diamondbacks came into this season expecting to make another run at the division title.