Magic coach Stan Van Gundy said before Sunday's game that Barnes is feeling "better and he'll start."
Barnes had missed practice Saturday because of back spasms. The injury had recently flared up after Barnes was first hurt in Game 3 of the Magic's second-round sweep of Atlanta.
Orlando's defensive stopper is expected to switch off Paul Pierce and guard Ray Allen for most of the series. Van Gundy had announced those plans before Barnes was injured, saying Barnes was better suited to chase Allen on the perimeter.
Information from The Associated Press was used in this report.