The Celtics have done well to weather through Gordon Hayward's fractured ankle on the opening night of the season, and Irving is a big reason for Boston's success.
In his first year with the team, Irving is averaging 24.1 points per game on 47.3 percent shooting. Most impressively, Irving has seamlessly integrated into Stevens' offense. He's dishing out 5.0 assists against 2.4 turnovers per game.
Stevens has proved himself to be one of the NBA's best coaches, but losing Irving for a stretch would be a significant blow for the Celtics.
Boston sacrificed a lot of roster depth to acquire Irving and Hayward. Starting Marcus Smart at point guard isn't a bad contingency plan with Irving unavailable, but his absence would mean elevating Shane Larkin on the depth chart, which is less than ideal for a team aiming to finish atop the Eastern Conference.