Boldin told USA Today on Saturday he's unwilling to slash his salary in order to stay with the team, citing "principles."
"At no point, no matter how well I played, would I come back to the table and say, 'I need more money.' The contract that I signed was the contract that I intended to play out," he told USA Today.
Flacco said he supported Boldin's stance.
"Without him, we don't win the Super Bowl. He's a huge part of this team and someone I want to see back," Flacco, who signed a six-year, $120.6 million contract this offseason, told USA Today. "Obviously, when you're a player of his caliber, you believe you're worth a number and that's what you should get. He's going to stick to his guns, and that's the way it should be."
Boldin is scheduled to earn $6 million in the coming season. He carries a $7.531 million salary-cap figure.
Fox Sports reported earlier Saturday that Baltimore gave Boldin an ultimatum: Take a pay cut or get cut on Tuesday. USA Today later reported that Boldin had rejected Baltimore's offer but that the sides were still discussing the matter, and that Boldin is prepared to test free agency if Baltimore releases him.
Boldin declined to confirm to USA Today that he had rejected a pay cut. He told ESPN's Adam Schefter on Saturday that the Ravens have not asked him to restructure his contract.
Boldin, 32, said last month that he would retire if he was cut by the Ravens. However, on Saturday, he changed that stance, saying he would discuss his options with his family if he were to be released.
In the playoffs, Boldin caught 22 passes for 380 yards receiving (95 yards per game) and four touchdowns. He has led Baltimore in receiving yards in each of the past three seasons since being traded from Arizona.
Boldin and Flacco made their comments to USA Today in Arizona, where they were participating in a charity function hosted by former quarterback Kurt Warner.
Information from ESPN.com AFC North blogger Jamison Hensley was used in this report.