SAN DIEGO -- From beginning to end, it was not a good day for the San Diego Padres.

It began with Bud Black getting fired after eight-plus seasons as manager, and it ended with the Padres being routed 9-1 by the Oakland A's in an interleague game at Petco Park.

"It was a weird vibe coming into the clubhouse today," losing pitcher Tyson Ross said. "I can't say enough about that man, he took me in at the low point of my career and believed in me."

Dave Roberts, who will manage the Padres until an interim manager is selected later in the week, said, "Obviously, what happened was unexpected for a lot of us in the clubhouse, but it had no bearing on the game."

A's catcher Stephen Vogt certainly had a bearing on the game. So did Oakland's starting pitcher, Jesse Hahn, a former Padre.

Vogt hit a grand slam and drove in five runs with three of the A's

13 hits. Third baseman Brett Lawrie added three hits and two RBIs.

Hahn (4-5) held the Padres to one run on three hits and two walks with four strikeouts over 6 2/3 innings.

"I was very excited for this start, but I really didn't change anything," said Hahn, who was 7-4 with a 3.07 ERA for the Padres last season before being traded to Oakland on Dec. 18 in a deal that brought catcher Derek Norris to San Diego. "I just treated it as another start."

Vogt's second career grand slam -- and 12th homer of the season -- capped a five-run eighth inning off Padres right-handed reliever Cory Mazzoni.

"I went up there in my first at-bat tonight and had a lackluster swing," Vogt said. "I wasn't really feeling aggressive. So I said I'm just going to swing as hard as I can, and when you hit a true line drive the other way, it reminds you that you know how to hit."

Monday's pitching matchup featured two right-handers who began their major league careers with the other team. Ross was the Athletics' second-round pick in the 2008 draft.

Ross experienced arguably his worst outing of the season, giving up four runs on seven hits and five walks with six strikeouts in five innings. Ross walked Ben Zobrist three times, and the A's left fielder scored after two of the free passes.

After pitching out of jams in the first and second, Ross allowed five consecutive A's to reach base in the third.

Second baseman Eric Sogard, who began his career in the Padres' minor league system, singled with one out, stole second and scored on right fielder Josh Reddick's single. Zobrist then drew his second walk ahead of a run-scoring single by Vogt. Lawrie made it 3-0 with a single.

The Padres got on the board in the bottom of the third when center fielder Will Venable doubled home shortstop Alexi Amarista after the Padres lost an appeal of Venable being hit by a pitch.

It appeared that Venable was grazed by a Hahn fastball, but plate umpire Mike DiMuro ruled the pitch didn't hit Venable, a decision that was upheld after a 2 1/2-minute review.

Venable returned to the plate and drove Hahn's next pitch over the head of center fielder Billy Burns, scoring Amarista, who drew a walk to open the inning.

Venable's double was the Padres' lone hit until Norris opened the seventh with an infield single.

Meanwhile, Oakland widened its lead to 4-1 in the fifth when Zobrist drew a one-out walk and came around on singles by Vogt and Lawrie.

NOTES: Bud Black was the first manager fired by the Padres during a season since Jim Riggleman replaced Greg Riddoch 150 games into the 1992 campaign. ... Padres OF/1B Wil Myers went back on the 15-day disabled list Monday with a return of the left wrist tendinitis that sidelined him for 28 games from May 11 through Thursday. San Diego recalled RHP Cory Mazzoni from Triple-A El Paso to take Myers' roster spot. ... A's RHP Edward Mujica (broken right thumb) began a rehab assignment with Class A Stockton on Mon