Larkin suffered a sprained shoulder when he collided with Philadelphia 76ers center Joel Embiid in Game 4.
Stevens said imaging tests appeared to indicate that Larkin won't require surgery. He said Larkin's shoulder is "very, very sore."
"Obviously he'll continue to strengthen it and work on it with our training staff and everything else," Stevens told reporters. "But I don't anticipate him back any time soon."
Larkin was averaging 3.7 points and 1.8 assists in 11 games this postseason.
Despite the modest stats, Larkin provided quality backcourt depth during the postseason with Marcus Smart and Jaylen Brown missing games and Kyrie Irving done for the season.
"We're just going to have other guys step up," Stevens said. "We're used to that. At the end of the day, that is what it is.
"He's played really well in this series. And he's done a lot of great things for us all year and through the playoffs. Bummer for him."
Boston leads the series 3-1 and will attempt to clinch it on Wednesday night. The Cleveland Cavaliers await in the Eastern Conference finals.
--Field Level Media