CINCINNATI -- Three solo homers. A two-run shot. A three-run shot. A pinch-hit grand slam. The Reds did it all, connecting every which way off a pitching staff that has never seen anything like it.

Todd Frazier and Zack Cozart each homered twice, and the Reds hit six in all -- including Xavier Paul's pinch grand slam -- while sending the Nationals to a 15-0 defeat Friday night, their first loss of the season and their worst loss since returning to Washington as a team.

"There was something in the air tonight," Paul said after his first career grand slam. "We were able to put 15 runs on the board, and not many teams have done that against the Nationals."

The Nationals swept their opening series against Miami by allowing only one run in three games. They were helpless against Cincinnati's surprisingly powerful offense -- nine homers in the last two games, though none by Joey Votto or Jay Bruce.

Everyone else is piling them up.

"A lot of people were questioning our hitting after the last series, even though we won two out of three," Cozart said. "Tonight, we showed that we can hit. Hopefully, we'll keep it going this weekend."

The series matches the NL's top two teams from last season. Washington led with 98 wins, followed by the Reds with 97. The teams have a history of close games -- four of their last eight had gone to extra innings.

This one quickly turned into a rout in one of the majors' most homer-friendly ballparks. The Reds had 19 hits, including a single by reliever Manny Parra, and finished with more homers than the Nationals had hits (5).

It was the Nationals' most lopsided loss since baseball returned to Washington in 2005, topping a 15-1 defeat to Detroit on June 19, 2007, according to STATS LLC. Washington had been the last major league team without a loss this season.

"I've had my share of bad games along with good games," said Dan Haren, who gave up four homers in his Nationals debut. "They're tough to deal with, but the sooner you forget about it, the better.

"It's such a long season. I've probably got 30-plus starts left. This start isn't going to define how the year goes."

Haren (0-1) signed a one-year, $13 million deal in the offseason, joining a formidable pitching staff that threw shutouts in the first two games of the season. It all came apart in Cincinnati's most lopsided shutout win since a 17-0 victory over Milwaukee at Cinergy Field on Aug. 7, 1998.

Homer Bailey (1-0) gave up two hits in six scoreless innings. The right-hander hasn't allowed a run in his last 19 regular-season innings, a streak that includes his no-hitter in Pittsburgh on Sept. 28. He gave up a run during the playoffs.

Bailey even got a double, too.

"That's when you know the team is having a good night, when I get a hit," Bailey said.

Frazier hit a solo shot into the upper deck in the second inning. On the next pitch, Cozart broke his 0-for-11 slump to start the season with a homer that a fan caught at the top of the wall in left field. Nationals manager Davey Johnson talked to the umpires about fan interference, but they declined to review it and stuck with the call.

It would be that kind of a night for the Nationals.

Cozart hit a three-run homer off Haren in the third, giving him two homers in three pitches from the right-hander. It was his first career multihomer game.

Shin-Soo Choo added a solo homer in the fourth that barely cleared the wall in center as a fan reached to catch it. Johnson asked for a review of that one and got it. Three minutes, 39 seconds later, the umpires upheld their call.

Cozart got his career-high fifth RBI on a sacrifice fly. Frazier added a two-run homer in the seventh, his third in two games. Paul's pinch-hit grand slam off Henry Rodriguez made it 14-0.

Game notes

The Reds will honor Johnson with a gift on the field before Saturday's game. Johnson managed the Reds to a division title and the NL championship series in 1995, but former owner Marge Schott replaced him with Ray Knight. The Reds didn't win another division title until 2010 under Dusty Baker. ... The Reds have fanned 43 batters, a club record for the first four games of a season. ... A fan ran onto the field and slid into second base during a pitching change. The man ran into the outfield before police tackled and handcuffed him.