Cincinnati, OH – Alfonso Soriano drove in three runs, while 8, in the opener of a four-game set.
Castro continued his breakout campaign with his ninth home run of the season, one of three hit by the Cubs and one of seven on the night. Aramis Ramirez finished 3-for-5 and hit his 25th home run of the campaign for the Cubs, who have won three straight.
Rodrigo Lopez (5-6) gave up five runs on nine hits with four strikeouts and one walk over 5 1/3 frames, but it was good enough to halt a three-decision losing streak.
Dontrelle Willis (0-6) remained winless on the season after giving up eight runs on nine hits with three walks over 3 1/3 innings. The southpaw didn't strike out a batter for the Reds, who have dropped three in a row and six of nine. Brandon Phillips hit two home runs in the loss.
"He (Willis) didn't have his fastball location," Reds manager Dusty Baker said. "The ball wasn't sinking like it usually is. He left some balls up and they hit him pretty hard. They hit everybody pretty hard tonight."
The Cubs put together a string of hits to jump on Willis early. Castro walked and Reed Johnson singled to center before Ramirez drove a run-scoring double that bounced off the rim of the track down the left-field line. Jeff Baker then walked and Soriano's chopper found space between third and shortstop, scoring Johnson. After a force out at home, Geovany Soto's slow roller forced Marlon Byrd at second, but Baker scored for a 3-0 lead.
Cincinnati came back with a pair of tape-measure shots in the second. Juan Francisco drove the ball out of Great American Ball Park, pulling a down-and-in pitch that traveled 502 feet and cleared the right-field stands.
Willis helped himself with a two-out single, giving Phillips a chance, and he delivered with an upper-deck shot for a 3-3 contest.
Chicago again got to Willis in the third, beginning with Baker's opposite- field solo shot to right, and the Cubs extended the frame thanks to Byrd's two-out single. Soto followed with a long drive to left center that bounced off center fielder Dave Sappelt's glove, allowing Byrd to score for a 5-3 game.
Willis was sent to the showers in the fourth, as the Cubs tacked on to their lead. Darwin Barney singled before Willis' wildness continued with a free pass to Lopez. Castro's double to right scored Barney, then after a fielder's choice at the plate, Ramirez chased Willis with an infield hit. After new hurler Jared Burton struck out Baker, Soriano came through with a two-run double down the left-field line for an 8-3 game.
"I expect that," said Soriano. "I believe I can hit with runners in scoring position."
Castro's two-run homer in the top of the fifth pushed the edge to 10-3, and Phillips tried his best to equalize with his second of the game, a solo shot to left in the home half.
Ramirez started the sixth frame with his 25th home run of the season to open an 11-4 edge. Another home run, this one a MLB-first for Devin Mesoraco, made it a six-run game in the home half.
Castro again triggered the offense in the eighth, doubling on a ball off the glove of Yonder Alonso in left and scoring on Johnson's single to center. The Reds scored on a pair of runs in the home half on Francisco's RBI groundout to first and Paul Janish's sacrifice fly.
Joey Votto's RBI double in the ninth capped the scoring.
Castro extended his hitting streak to 13 games and has now reached base safely in 25 straight games..Francisco's home run hit onto Mehring Way...It was the second longest home run in Great American Ball Park history, only behind Adam Dunn's titanic 535-foot shot that landed in the river during a 2004 game against the Dodgers...Votto extended his hitting streak to six games...Phillips recorded his eighth career multi-homer game...Cincinnati still narrowly leads the season series, 8-7.