Steady showers began about 45 minutes before the scheduled start time of 1:35 p.m. and continued through the official announcement of the postponement at about 2:45. The game will be made up as part of a doubleheader Aug. 28.
Sunday was the third postponement due to rain for the Pirates at home this season, plus a suspended game May 1 that was finished the following afternoon. The first two were April 14-15 against the Giants, which made necessary an Aug. 13 doubleheader.
The Reds had taken the first two games of the weekend series.
Scheduled Pirates starter Tom Gorzelanny has not pitched since leaving his start July 25 in New York in the third inning complaining of left shoulder stiffness. The rain out, combined with a scheduled off day Monday, means he will have an extra 48 hours to rest.
"I have been able to get a lot of work in since my last start," Gorzelanny said. "And my arm feels so much stronger."
The Reds were in a similar situation with right-hander Aaron Harang, who has not started since July 28 and left after one inning due to a sore lower back. He was scheduled to start Thursday against Los Angeles, but Reds manager Pete Mackanin said he might be pushed back to Wednesday.
The team was to evaluate the situation during its plane ride back to Cincinnati and would make an announcement about the rotation on Monday. Bronson Arroyo was supposed to start Sunday, but the Reds indicated he might be moved to Wednesday to allow Harang to continue his pattern of preparation and start Tuesday.
Pitchers aren't the only ones who will likely benefit from the extra time off. Pirates outfielder Xavier Nady was not in the lineup again Sunday -- the fifth consecutive game he did not start due to a strained left hamstring.
"Nady was out running with (trainer Brad Henderson) today, just to see how far along he is," Pirates manager Jim Tracy said. "His leg is not to the point yet where you can consider sending him out there."
Reds outfielder Ryan Freel left Thursday's game in Washington with a sore right knee and is officially listed as day-to-day. Mackanin said that if Freel's condition does not improve in the next 24 hours, a second trip to the disabled list for him this season is possible.
Freel's injury was one of the reasons Jeff Keppinger was poised to make his first career start in the outfield.
Keppinger, who has started games at all four infield positions during his 58-start major league career, played one inning in left for the Kansas City Royals last season. He has six hits in his last 15 at-bats, and hit a game-tying homer in the ninth inning Saturday night.
"He told me he's comfortable (in left), and we want to find ways to keep his bat in the lineup," Mackanin said.
Regular leftfielder Adam Dunn had homered in each of his past three games, but Mackanin did not want him to have to face Gorzelanny.
"He likes to play every day and compete against lefties," Mackanin said. "But sometimes, it's good not to have to face that tough left-hander that can maybe screw up your swing a little bit."
Gorzelanny will start Tuesday in Arizona, but Tony Armas will be skipped in the rotation, meaning that Matt Morris will still face the team that traded him Tuesday, the San Francisco Giants, in only his second start for Pittsburgh on Friday.
Rookie Shane Youman will make a spot start during a doubleheader in Pittsburgh against the Giants Aug. 13. He was removed from the rotation when the Pirates acquired Morris.