After the Boston Celtics won the opening tip, Paul Pierce drove into the lane for a lay-up and missed. Kevin Garnett then grabbed the rebound and missed a shot in the paint. Pierce grabbed yet another offensive rebound and kicked the ball out to Avery Bradley in the corner. He missed as well.

The first 20 seconds of Friday night’s Game 3 between the New York Knicks and host Celtics was a microcosm of the remaining 48 minutes. Once again inept on offense, the Celtics now trail the Knicks 3-0 in the best-of-seven series with Game 4 on Sunday afternoon at TD Garden.

“I thought they wanted to play well,” Doc Rivers said of his team before relenting, “we did lose our spirit early on.”

The final score, 90-76, didn’t fully represent how effectively the Knicks took away the home team’s spirit. After the game, the Celtics looked exhausted and defeated.

“They’ve been playing hard, but we’ve just forced them into tough situations defensively, and have been able to wear them down,” Tyson Chandler said.

Rivers tried to reinvigorate his team after back-to-back losses in New York, starting Jason Terry and sending Brandon Boss to the bench, but the move proved futile. Terry, who has struggled in the series, did little more than he did in the previous two games. He scored 14 points, but eight came long after the game had been decided.

Terry left Pablo Prigioni open often in the first quarter and the Knicks took advantage as the Boston defense failed to pressure the three-point line. New York took five of their first eight shots from deep and went 11-for-27 overall.

Garnett came to play, as you might expect, but it didn’t matter. Nothing could wake the Celtics from their offensive slumber. After averaging 96.5 points per game in the regular season, the Celtics have managed just 75 per game in the playoffs.

“Just play together,” Jeff Green said when asked how the Celtics can rectify things. “We got a lot of easy looks tonight. We missed a lot of easy layups. I think we let that affect us on the defensive end.”

Garnett finished with 12 points and 17 rebounds, but Paul Pierce was largely ineffective. He had 17 points on 6-for-15 shooting, five assists, four rebounds and an unsightly five turnovers. Through three games, Pierce has 16 turnovers. Rivers got the sense in the second half that Garnett was trying to will the Celtics back into the game, to no avail.

“He was getting frustrated, because he wanted them to be him,” Rivers said. “In the same spirit, but he just kept chugging along. He didn’t change. He didn’t change his demeanor. He’s as competitive of a human being as I’ve ever been around.”

The only life the Celtics showed came midway through the fourth quarter when Terry tried to go after J.R. Smith following a flagrant foul by the NBA’s Sixth Man of the Year. Smith was ejected after the foul was ruled a Flagrant II and Terry’s teammates kept him from reacting aggressively and compounding the loss.

Aside from touching tributes to the first responders in last week’s Boston Marathon bombings and midcourt ceremonies to honor those in Watertown, Mass., nothing went right for the Celtics. They couldn’t even keep score properly. Carmelo Anthony, who had 12 points in the first half, was shown as having only four on the JumboTron. The error was fixed at halftime, but the Celtics were not.

Courtney Lee, buried on the bench for the first two games, got into the game early. In 11 minutes, he couldn’t jumpstart anything. Terrence Williams found himself on the court in the second half, but that prayer would not be answered. Rajon Rondo, he of the torn ACL, is not walking through that door and Rivers is simply out of options.

The Celtics lost three players -- Rondo, Jared Sullinger and Leandro Barbosa -- to season-ending injuries, but no one in the NBA will feel sorry for them. A number of teams, including the Knicks, have dealt with adversity and come out on the other side. This could be said going back as far as this offseason, but Danny Ainge wasn’t able to plug holes as well as his counterpart, Glen Grunwald.

Now, the Celtics, who many felt no one wanted to face in the first round, are a loss away from a sweep. Before long, the questions surrounding the team will have a much farther reach than just the scope of a poor playoff series.

“It’s a simple message,” Rivers said. “You’ve got to win the next one. It’s simple. And that’s where it starts.”