Braves manager Fredi Gonzalez announced his decision Thursday, saying that Ross gives Atlanta a "good chance to win a ballgame."
"It's been hard," Gonzalez said before a workout at Turner Field. "I've been thinking about this for three or four days. (McCann) is a very important part of our team and he's a warrior."
McCann, 28, batted a career-worst .230 this season and was bothered by shoulder and hamstring injuries throughout the year. Gonzalez stressed that McCann will play if the Braves advance to the NL Division Series.
"I think going forward Mac will catch, obviously, in a longer series, a five-game series or even a seven-game series if we get that far," Gonzalez said. "We'll play the matchups."
Gonzalez said that Ross, an 11-year veteran, is better equipped to play against the Cardinals, who traditionally are aggressive on the basepaths. Also, Ross was behind the plate for two of the most dominant performances by starting pitcher Kris Medlen -- a 12-strikeout effort against Colorado on Sept. 3 and a career-high 13 Ks against Washington on Sept. 14.
"Defensively, we know how well (Ross) can throw people out," Gonzalez said. "The Cardinals have a tendency to put people in motion a lot. With the combination of (Ross) and Medlen, maybe we have an opportunity to shut that down a little bit."
Ross, 35, batted .256 with nine home runs in 62 games this season. He threw out 44 percent (15-for-34) of would-be base stealers this season, while McCann threw out just 24 percent (24-of-100).
Gonzalez said Ross, a right-handed hitter, could start again if the Braves advance to face Washington and left-hander Gio Gonzalez, since McCann bats lefty. But the manager stressed that McCann will get the bulk of the playing time if Atlanta makes an extended postseason run.
"He's beat up. He's been banged up for a while," Gonzalez said. "Again, a one-game series, you go with Rossy. In a longer series, (McCann is) going to play. He's not that banged up."
McCann said he understood Gonzalez's decision to start Ross and acknowledged that he likely will undergo shoulder surgery in the offseason.
"I have not played the way I want to play," McCann said. "Ross has been playing great."
Asked about McCann's reaction, Gonzalez said, "He understands. It's tough for both of us, you know? But he understood."
Information from The Associated Press was used in this report.