WALTHAM, Mass. (AP) — Hanging on a wall of the Celtics' practice facility, opposite the faded banners that hung in the old Boston Garden a half-century ago, is a spotless one.

It went up a few years ago to hold the location where the NBA's greatest champions would mark their next title.

That banner will apparently remain blank another year. As soon as Sunday, the Celtics' quest for No. 18 could be over for this season.

Down 3-0 to the New York Knicks, the Celtics are thinking much smaller than another title when they host Game 4 on Sunday afternoon.

"You've got to focus on the single game. You can't win four without winning one," Boston coach Doc Rivers said Saturday.

Even that looks difficult for a Celtics team that can't get any offense going. Boston has averaged a feeble 75 points, not breaking 80 in any game, on 39.5 percent shooting.

No NBA team has overcome a 3-0 deficit to win a series, as the Knicks know. They were swept by the Celtics two years ago and managed only to get to Game 5 after dropping the first three against Miami last year, when they ran their NBA-record postseason losing streak to 13 games.

Now Carmelo Anthony sees the Celtics in the same position he was in during his first two postseasons in New York, and he wants the sweep.

"To be honest with you, to accomplish that would be spectacular. It would be a dream come true. I've never swept anybody. But we know Game 4 is win or go home for them guys," Anthony said.

"I've been on that side of the ball plenty of times and I know that feeling, so I know the type of energy they're going to come out and display here on Sunday. We've just got to be prepared for the punches that they throw and everything they put out there on the basketball court."

There haven't been any punches, though the Celtics' Jason Terry did take an elbow in the chin from New York's J.R. Smith late in Game 3. The NBA suspended Smith for Sunday's game.

Terry wouldn't comment on the play Saturday, but said he was annoyed by what he thought was some Knicks' showboating and is clearly agitated by what's gone on in the series.

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"I mean, when you get your butt kicked like they've been doing to us the last week or so and you're seeing the same team every day, you're going to get tired of it. Or you're going to lay down. I'm tired of it," Terry said.

The Celtics haven't lost in the first round since 2005 and haven't been swept since Indiana beat them in the first round a year earlier.

They returned to prominence six years ago when they acquired Kevin Garnett and Ray Allen to team with Paul Pierce, and it's been a good run for the Celtics. They won a title in 2008, lost in a Game 7 to the Lakers two years later, and pushed Miami to seven games in last year's Eastern Conference finals.

But Allen then joined the Heat, and All-Star point guard Rajon Rondo was lost to a knee injury around midseason. Garnett will turn 37 next month and Pierce is 35, and the Celtics have had opportunities to trade both of them. There may be more decisions in the offseason, so the end of this series could actually be the end of an era.

"I dread the end all the time. I really do," Rivers said. "I just like to be able to know when the end is, meaning you're in Game 7 of the world championship. Then you know you're playing for the end. I hate when the end can come early. But I dread them all."

Game 5 would be Wednesday, though the Knicks would prefer to wrap it up Sunday and give one of the oldest rosters in NBA history some extra rest before their first appearance in the second round since 2000.

"For sure," said point guard Raymond Felton. "Just like Melo said, I've been on the other end of the stick as well. I was in Charlotte, made the playoffs for the first time and we got swept by Orlando. So it feels good to be on the winning side. So if we could come out and definitely sweep this game, it would be something special for all of us. For me, for him, especially individually, and then on top of that we'd get a lot of rest. And hopefully Indiana and Atlanta can go to Game 7."

The Celtics believe they can turn things around with more effort, though their execution has been just as poor. Not even Pierce has been immune to their woes, missing a layup on the first possession of Friday's 90-76 loss and just fumbling the ball away on a couple of occasions later in the game.

But forward Jeff Green said his confidence is "still high," even if the Celtics' chances of advancing aren't.

"I mean, look at the guys on this team, guys who have been through so much throughout their career," he said. They've been down. I mean you have guys who are confident in their game and believe that we have a chance, and that's all that it takes."

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