Padres fire Bud Black

— -- SAN DIEGO -- The Padres fired longtime manager Bud Black on Monday after hovering around .500 with a roster that was overhauled in the offseason.

The team said that it was immediately beginning a search for an interim manager to take over for the rest of the season.

Bench coach Dave Roberts, a former Padres outfielder, was tapped to serve as manager when the Padres host Oakland on Monday night.

A source told ESPN's Keith Olbermann that Pat Murphy, the manager of the Padres' Triple-A team in El Paso, Texas, is en route to San Diego. It's unclear whether Murphy will become the team's manager or fill in as bench coach as Roberts moves to interim manager. In fact, according to a source, Murphy himself doesn't know, for certain, what his role will be.

The Padres entered the season expecting to contend in the National League West but are trying to get out from under .500. They are 32-33 heading into Monday night's interleague game against Oakland.

Black had been San Diego's manager since 2007, was 649-713 and failed to reach the postseason. The Padres, who are six games out in the division, made attention-grabbing additions in the offseason, including outfielder Matt Kemp from the Dodgers and right-hander James Shields in free agency. Yet the moves haven't translated to success in the win column.

Black matched Bruce Bochy as the longest-tenured manager in the NL. The Angels' Mike Scioscia, hired in 2000, is the game's longest-tenured manager.