BOSTON — The shock of the Marcus Smart injury diagnosis had to be shaken off quickly. The thought of going into a playoff battle without the heart of their defense isn’t great for the Boston Celtics, but a referee is tossing that ball up Sunday afternoon for Game 1 of the playoffs, no matter what.

“I just think that’s part of it,” Coach Brad Stevens told reporters. “You prepare all NBA season to be ready for that. How many games did we have our full group together, especially after the first 15 or 20? That’s part of it.”

This is the NBA’s survival of the fittest. This herd has no choice but to move forward, no matter what’s happening to thin their numbers behind them. Smart’s uniqueness adds a higher level of difficulty to this quest.

There is no one person with all of Smart’s attributes, and since no technology exists outside of a Disney movie to switch Smart’s mentality into another person’s body, the job of filling the void will fall on more than one person.

“We want everybody to play within what we’re trying to do to their individual strengths,” Stevens said. “I just think ultimately whoever is playing together needs to focus on what their jobs are, control what they can control, and that’s that. Nobody’s going to be Marcus Smart. We don’t expect anybody to be Marcus Smart.”

Terry Rozier expects to be one of the players who take on a larger role in the Celtics’ first-round series against the Indiana Pacers.

“I feel like I’m more important to the series now, I’m more needed,” Rozier said. “Obviously I’m going to have to step up. I’m gonna be ready for it.”

Rozier seemed to be in line for a reduction in minutes. The March 29 game against the Indiana Pacers, where both teams were fully healthy and battling for playoff position, may be the best indicator of what Stevens was planning. Rozier played 15 minutes in that game, but even some of those could have been chopped.

“Everybody has to be ready when the playoffs come because everything else is out the window,” Stevens recently said. “It’s who gives you the best chance at winning.”

Rozier wasn’t often giving Boston its best chance at winning during the regular season. His -1.2 net rating is the lowest of any regular rotation player on the team. If he’s going to be part of the solution, he’s going to have to clean up a lot of the bad habits that turned him from last year’s playoff hero to the source of fans’ ire this season.

“I’m going to go out there and play my game. I’m not going to try to imitate nobody else or be nobody else, be somebody that I’m not,” Rozier said.

“It’s tough making up for a guy like Smart, the things he’s capable of doing out there, but we’ve got to move on.”

Someone is going to have to assume Smart’s spot in the starting lineup, and someone will get minutes behind that player.

“I’ve got an idea, but I’m going to see how the next couple of days play themselves out, too,” Stevens said of picking a new starter.