Coach Mike Smith says Ryan will need three to four weeks to recover from the injury, which was described as a sprained AC joint to the non-throwing shoulder. No surgery is required.
An MRI exam on Ryan's left shoulder confirmed a Grade 2 AC joint sprain, a league source told ESPN. Ryan will be in a sling for approximately 10 days.
Ryan was hurt just after the two-minute warning. On a 5-yard pass that Jason Snelling took down to the San Francisco 10, linebacker Ahmad Brooks got a shot on the Atlanta quarterback. Ryan's next two passes were incomplete, sealing the 49ers' 28-24 victory.
Smith says Ryan would've played if the Falcons had beaten the 49ers and advanced to the Super Bowl in two weeks.
Despite passing for a postseason franchise-record 396 yards and three touchdowns, Ryan committed two costly turnovers in the second half.
On Sunday, Ryan said his shoulder was "good enough to go" late in the game, despite his injury.
Information from ESPN NFL Insider Adam Schefter and The Associated Press was used in this report.