"What we decided is that going forward next week we are not going to start Daisuke," Francona said.
Citing potential health issues with the Japanese import, Boston's $100-million investment, Francona announced before the game that Matsuzaka was to be evaluated by team physician Thomas Gill and Red Sox trainers.
Following the Red Sox's 3-0 victory over the Braves, Francona said Matsuzaka underwent an MRI on Saturday night. While the test revealed no structural damage in Dice-K's right shoulder, Francona reported unspecified "weakness" in the pitcher that will be addressed over the next few days.
Matsuzaka spent time on the disabled list earlier this season with a mild right shoulder strain, but Francona was non-committal when asked about a return trip to the DL for the righty.
"We don't have anything official to announce, because we really need to let this thing settle down," Francona said. "But there is no official announcement tonight."
A two-time Most Valuable Player of the World Baseball Classic, which deprived Matsuzaka of a normal Spring Training with the Red Sox this season, Dice-K has not registered a quality start in eight outings (1-5, 8.23 ERA).
"It all started with the WBC and him not having a consistent base," Francona said. "We've been fighting that all year, and we'll continue to. But instead of just taking a guy out of the rotation, we want to fix it.
"The idea is to make this better, and we're working on that."
With John Smoltz set to make his first start of the season Thursday in Washington, talk of a six-man rotation has quickly been shifted to the backburner. In the interim, the Red Sox find themselves in a holding pattern with the enigmatic Matsuzaka, a Cy Young Award candidate just one season ago.
"I've watched him for three years now," Francona said, "and it looks to me like he's struggling to get the velocity he could before. He ramped up pretty quick to pitch in [the Classic] games that meant a lot to him, and I understand that. But there wasn't that base to build off of for the entire season. I'm actually not surprised [with the struggles].
"I do think he's searching. This has been tough for him. I certainly acknowledge that, and I think he does too."