SAN DIEGO -- The San Diego Padres' slump has gotten so bad that a disenchanted fan stood up during the sixth inning Sunday and started yelling, "Let's go Chargers, let's go," a chant that rang out through the quiet ballpark.
The Padres aren't quite ready to make way for the city's NFL franchise, but they haven't exactly been playing like a first-place team for most of the summer.
And on Sunday, they technically weren't a first-place team anymore.
Adam Dunn hit a grand slam in the fifth inning, Cincinnati's third homer of the game, and the Reds beat San Diego 7-1 to drop the Padres percentage points behind the Arizona Diamondbacks in the sad-sack NL West.
Wily Mo Pena and Rich Aurilia also homered to complete the three-game sweep for the Reds, who have won a season-high five straight.
The Diamondbacks (52-55, .4859) won 13-6 at the Chicago Cubs to leapfrog the Padres (51-54, .4857) atop baseball's worst division. The Padres had led the West since May 26, when they were 28-19 and one-half game ahead of Arizona.
"We know we're awful," manager Bruce Bochy said. "We're embarrassed, to be honest. We've got to keep coming out here and getting after it. We have no choice.
"Right now it's like a virus has hit our bats and now it's hit our staff a little bit. We've got to get this thing cured, and quick. It's gone on too long."
The Padres went 22-6 in May to set a franchise record for wins in a month and climb to 14 games over .500. Their luck changed along with the calendar, although the division is so weak that it's taken this long for a change at the top.
The Padres have lost 12 of 13 overall and 35 of 53 since June 1. Clutch hits and home runs have practically disappeared, and their bullpen is running on fumes because starters haven't been going deep into games.
Woody Williams allowed all three homers Sunday.
"I take full responsibility today," Williams said. "There should be no fingers pointed but at me."
Asked about surrendering the division lead, he said: "Maybe it'll help us relax a little bit and go out there and play a little bit better brand of baseball."
The Reds outscored San Diego 24-5 and made spacious Petco Park play like a bandbox. The Reds outhomered the Padres 8-0 and outhit them 33-18. The Reds had 21 extra-base hits while the Padres had just four.
"Our team is going to hit home runs regardless," Dunn said. "It's a big park but I don't think that the park really matters."
Dunn went 6-for-14 with three homers, two doubles and nine RBI in the series.
The Padres also lost two of three to St. Louis during the homestand, when they were outscored 40-12 and outhomered 11-0.
"We'd like to think we are going to run into some balls," Bochy said. "We're getting outslugged."
San Diego has gone eight games without a homer. The Padres failed to connect off Eric Milton, who leads the majors with 31 homers allowed.
Milton (5-11) threw seven scoreless innings, allowing four hits while striking out six and walking none. He retired 16 of his final 17 batters and lowered his ERA from 7.03 to 6.65.
"That's the best I've felt all season," Milton said. "Today was good for me to throw up zeros like that. Today was really what I've been looking for."
Williams (5-8) lasted only five innings, allowing seven runs and seven hits, including all three homers. He struck out seven, but two of his three walks came ahead of Dunn's slam, which was the first since Petco opened last season.
Williams walked Milton leading off the fifth, allowed Felipe Lopez's single with one out and then walked Sean Casey before Dunn drove a 2-2 pitch deep into the seats in right field, his 31st. It was his second slam of the year and fifth of his career.
"I've faced Woody for a long time and he owns me," Dunn said. "I can't figure him out. He was throwing me in the whole time and I think he just left one out over the plate."
Pena homered to straightaway center with one out in the second, his 13th. San Diego's Damian Jackson leaped vainly for the ball and almost tumbled over the fence.
Aurilia hit a two-run homer into the balcony on the fourth floor of the Western Metal Supply Co. brick warehouse just beyond the left-field corner with one out in the fourth. It was his 11th, and Casey was aboard on a leadoff double.
San Diego scored an unearned run on Mark Loretta's groundout in the eighth.
Dunn's other grand slam this year was July 9 at Arizona. ... The Reds are undefeated in their last seven series, with four wins and three splits. ... The Reds were 17-11 in July, their first winning month since May 2004 (18-11). ... It was just the third time this season Milton pitched seven or more innings. ... Padres 1B coach Davey Lopes was absent due to an illness in his family. ... The last time Cincinnati had a three-game sweep in San Diego was June 10-12, 1996. The Padres slumped that June but then won the NL West.