Jeff Samardzija (2-1, 4.13 ERA) and Bronson Arroyo (1-0, 2.70 ERA), who were scheduled to start Tuesday, will face each other on Wednesday at 6:10 p.m. CT at Great American Ball Park. Ryan Dempster (0-1, 1.33 ERA) will face Homer Bailey (1-2, 3.60 ERA) on Thursday in the series finale.
Samardzija already had been given one extra day of rest after being pushed back in the Cubs' rotation order. He played catch in the outfield on Tuesday shortly before the game was officially called after a 2-hour, 13-minute wait.
"He's had plenty of rest," Cubs manager Dale Sveum said.
With the postponement, Paul Maholm (2-2, 6.20), who was to start Wednesday, now will get extra time and start on Friday to open the Cubs' series against the Dodgers at Wrigley Field.
The postponement gives the Cubs' bullpen a chance to recover. Scott Maine has been sick, even though he was able to pitch on Monday. Rafael Dolis was unavailable Tuesday but will be ready to go Wednesday, Sveum said.
The Cubs entered the game 5-4 in their last nine games after a 3-11 start to the season. Bryan LaHair has provided most of the spark. He has 13 RBIs in his last 13 games, and of his five home runs, three have tied the game and one gave the Cubs the lead.
This is the second series this season between the Cubs and Reds, who played at Wrigley Field from April 20-22. Cincinnati took two out of three games in that series.
The Cubs return to Cincinnati again Aug. 17-19.
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter@CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.