The Padres, who dropped to 32-44 following a loss to the Dodgers, dismissed Byrnes following two-plus seasons as general manager of the team shortly before first pitch on Sunday.
Only the D-backs trail the Padres in the National League West, with the first-place Giants 13 1/2 games up on San Diego. There are 10 teams ahead of the Padres in the NL Wild-Card race.
Byrnes wasn't immediately available for comment Sunday.
The Padres have scored the fewest runs in baseball. They have scored 225 runs this season -- or 42 fewer than the 29th ranked team (Braves). They also rank last in the big leagues in batting average (.214), on-base percentage (.274), and slugging (.339).
There had been rumblings and rumors locally that the team was considering changes, either up top with Byrnes or possibly manager Bud Black. Mike Dee, team president and CEO of the Padres, said the Padres will keep Black at least through the end of the season.
"This was a decision that was not made in a day or two or a week or two. The last couple months, we've seen a team we had high expectations for. Those expectations have not been reached," said Dee.
Assistant general managers A.J. Hinch and Fred Uhlman Jr. and Omar Minaya, the senior vice president of baseball operations, will oversee the general manager duties on an interim basis.
Dee said the search for a new general manager "begins immediately." And while Hinch and Minaya will certainly merit consideration, there seems to be a sentiment that the hire will come from the outside -- and, quite possibly, could occur soon.
"I think this is a pretty juicy job for someone who wants to be a general manager," Dee said. "… It will be someone with a near-, mid- and long-term vision of what we want to be as an organization."
Boston assistant general manager Mike Hazen, who has a history with Dee, will likely figure prominently on the Padres' wish list. He's been a farm director and has a wide base of front-office experience going back to his days working with the Indians.
Billy Eppler, assistant general manager of the Yankees and a San Diego native, fits the bill of someone who could be a name of interest.
When he was hired in October 2011, Byrnes was the third GM in a three-year span. His tenure with the Padres rates as more favorable in terms of his trade history than any free agents or contract extensions that he helped broker.
Byrnes was hired by the Padres as their vice president of baseball operations on Dec. 3, 2010, reuniting him with Padres executive chairman Jeff Moorad, the former CEO of the Diamondbacks.
Byrnes was hired by Moorad in Arizona in October 2005 and was later given an eight-year contract extension that would have taken him through 2015. But Byrnes was dismissed by the D-backs in July 2010.
On Oct. 26, 2011, the Padres promoted Byrnes to general manager, a move that saw Jed Hoyer, then general manager of the Padres, head to Chicago to serve in the same role with the Cubs. His deal was reported to be for five years with an option, running through 2017.
Lauded by his peers for being methodical, creative and also for his baseball acumen, Byrnes traded for pitcher Tyson Ross after the 2012 season and needed only to give the A's two Minor League players, Andrew Werner and Andy Parrino. In 51 games, including 32 starts, Ross has a 1.6 WAR with a 9-15 record and 3.19 ERA.
The Padres acquired closer Huston Street at the 2011 Winter Meetings from the Rockies for Minor League pitcher Nick Schmidt. Street has become one of the most dependable closers in the big leagues, compiling a 3.7 WAR with 94 saves with the highest save percentage (96.2 percent) in the game since 2012.
Under Byrnes, the Padres swapped popular first baseman Anthony Rizzo to the Cubs for starting pitcher Andrew Cashner, who looks the part of a frontline starting pitcher.
This past winter, Byrnes dealt another popular player, reliever Luke Gregerson, to the A's for outfielder Seth Smith, who has become the most reliable bat in the Padres lineup.
There have been deals that haven't worked out, too.
The five-player deal with the Reds in December 2011, one that saw the Padres ship pitcher Mat Latos to the Reds for four players, hasn't provided enough of a return. Catcher Yasmani Grandal, an important piece to the deal, was suspended for 50 games a year ago after testing positive for elevated levels of testosterone.
A handful of extensions done by Byrnes haven't paid off, as the team inked outfielder Carlos Quentin to a $27 million extension in July 2012 after trading for him on Dec. 31, 2011. Quentin has had three knee surgeries since he joined the organization and hasn't played in more than 86 games in his first two seasons with the team.
During Spring Training 2012, Byrnes agreed to pre-arbitration deals with three players -- pitcher Cory Luebke, outfielder Cameron Maybin and catcher Nick Hundley.
Since then, Luebke has had Tommy John surgery twice, Hundley was traded to the Orioles last month and Maybin played in just 13 games a year ago and has failed to match the offensive success he had in 2011, his first season with the team.
The Padres have also been plagued by a number of injuries to their top players; Chase Headley, Quentin, Jedd Gyorko, Yonder Alonso and Maybin have all missed time the last few years due to injury. The arms have been hit hard by injury as well, as Luebke, Josh Johnson, Casey Kelly and Joe Wieland have had Tommy John surgery.
This past winter, Byrnes rolled the dice and signed Johnson to a one-year deal for $8 million. Johnson, who had health issues last season with the Jays, suffered an elbow injury in Spring Training and later needed Tommy John surgery, the second in his career.
"It's tough when this happens," said Padres pitcher Ian Kennedy, who Byrnes traded for twice. "... The players are the reason we aren't performing up to our standards. Josh assembled the team, but we've still got to go out and play."
The Padres raised their payroll from $68 million to $90 million this season and the team signed off on a $35 million contract extension in April for Gyorko.
"You expect better performance. We gave baseball ops [operations] a clean slate as far as what they want and what they want to do," Fowler said. "We're standing here as a result of that not working."
As is the case with others in his line of work, some of Byrnes' deals and trades worked out. Some didn't.
Now the Padres will embark on finding another general manager to help lead the baseball side of the organization.
"We will hire great baseball people. We want baseball people with baseball experience to make baseball decisions for this organization. We want someone who wants to be in San Diego," Dee said.
"We are going to look forward, not back."