BOSTON (CBS) — Given the Celtics’ disappointing regular season, it’s somewhat fitting that the postseason began with a disappointment of its own. Marcus Smart will be out for the first round of the playoffs, and likely the second round, due to an oblique injury.

In the latest edition of the Slice of Sully, the impact of that loss was topic No. 1.

“It’s a huge blow,” Scott Sullivan told Steve Burton. “He’s like the backbone of this team. He’s not the best player at any part of the game, but he brings it every single night, and the team feeds off his energy. He is the best defender on the team, so you’re going to be losing that. He makes big plays at key times; you’re going to be losing that. … It’s such a big loss.”

When it comes to which player might step up in Smart’s absence, Sully is looking toward Gordon Hayward.

“I love the way Hayward’s played down the stretch. He’s looked really, really good. He’s aggressive again. You can tell, I think he’s gotten over the mental part of the injury, and he’s driving to the basket, he’s cutting, he’s making moves, he’s doing his thing,” Sully said. “I just enjoy watching his game. And if he’s aggressive and doing that, then that makes a big difference.”

Sully also discussed his expectations for Kyrie Irving, and gave his prediction for the Celtics’ first-round series against the Pacers.