The defending NL Central champions are tied for first place and barely over .500. Manager Dusty Baker isn't surprised.

Ryan Roberts got into Arizona's lineup because of an injury to Melvin Mora and hit two of the Diamondbacks' four homers off Sam LeCure, setting up a 5-4 victory on Tuesday night that extended the Cincinnati Reds' slide.

The Reds have lost five of six, falling to one game over .500 (9-8) for the first time since they beat Milwaukee on opening day.

Cincinnati opened the season 5-0 even though starters Johnny Cueto and Homer Bailey were on the disabled list with shoulder problems. Baker thinks it's finally catching up with them.

"You can't feel sorry for yourself," Baker said. "You've just got to keep playing. We knew it was going to be a tough road sooner or later, especially with Cueto and Bailey out."

For the third game in a row, a Reds starter gave up at least five runs. LeCure (0-1) lasted only 5 1-3 innings and gave up nine hits, including the career-high four homers. It was the most homers allowed by the Reds in a game this season.

"I felt like I made some pretty good pitches," LeCure said. "That first home run (by Roberts) went a long way the other way, and I thought, 'That's not a good sign.' I was trying to keep it down because if they got it up in the air, you just weren't sure.

"Every ball hit in the air I was scared about. Some of the balls they hit were down."

Roberts hit a solo drive and a two-run homer for his second career multihomer game. Kelly Johnson and Chris Young also connected, helping the Diamondbacks pile up a season high in homers.

Armando Galarraga went six innings, matching the best start of his career at 3-0. J.J. Putz pitched the ninth for his fourth save in four chances, fanning Chris Heisey with a runner on second to end it.

"Sometimes you score runs at will," Baker said. "Sometimes, you can't buy a run."

A sore foot unexpectedly played a role in the outcome.

Mora jammed his left foot while running the bases Sunday during a 6-5, 12-inning win over San Francisco. He tested it before Tuesday's game and felt some soreness, so manager Kirk Gibson made the lineup change as a precaution.

Turned out to be a fortunate break.

Roberts hit a solo homer in the first and a two-run shot in the fifth, when Arizona squandered a chance to pull away. The Diamondbacks had a single, a double, a triple and Roberts' homer in the inning, but managed only two runs.

Galarraga had a lot to do with it.

Juan Miranda opened the fifth with a double and Galarraga tried to sacrifice, but his bunt went right to LeCure, who was able to get the out at third. When Johnson followed with a single, Galarraga rounded second base too far and was caught in a rundown.

Roberts homered into the first row of seats in left field for a 4-3 lead. Justin Upton followed with a fly that deflected off the top of the wall in right field and came back, leaving him with a triple. The umpires reviewed the play and confirmed the call.

Cincinnati's Brandon Phillips singled home a run off David Hernandez in the eighth.

NOTES: Roberts' other multihomer game was Aug. 4, 2009, at Pittsburgh. ... Galarraga also won his first three decisions in 2009. ... Umpires took 2 minutes, 39 seconds to review Upton's triple in the fifth and uphold the call. Upton contended the ball had cleared the wall and bounced back. ... Putz is the first Diamondbacks pitcher to convert his first four save chances of the season. Mike Morgan converted three in a row in 2000. ... Baker will let RHP Mike Leake start the final game of the series on Thursday as planned. Leake was arrested on a shoplifting charge Monday. ... Phillips was back in the Reds' starting lineup after missing four games with a sore groin.