Danny Ainge is approaching today’s potential Celtics elimination with eyes wide open. That doesn’t mean he won’t throw a coin in the Great Fountain of Overwhelming Underdogs, but he fully understands what is going on here against the Knicks.

Put it this way, the president of basketball operations isn’t waiting for any CSI reports.

“Hey, listen, nobody likes being down 0-3,” Ainge said yesterday. “Nobody’s come back from 0-3. But there’s always a first time for something.

“But right now we’ve just been beaten in three games by a team that has played better. Their offense and their defense has been better than ours. Carmelo (Anthony) and J.R. Smith and Raymond Felton have been terrific and very challenging for us to match up with.”

Asked about his plans, Ainge smiled and said, “Win Game 4 and go back to New York for Game 5.”

Simple. . . . OK, maybe not.

The Knicks have proven more than the Celtics can handle, and Ainge believes the Celtics have exhausted most all of the strategies that can be written on a drawing board. He is well aware of his club’s offensive deficiencies, and he thinks they have come even further to light because things aren’t going so well at the other end either.

“We have had trouble even at full strength over the past few years with scoring in the fourth quarter, and our defense has been our identity,” Ainge said. “We have been a defensive-minded team. Even in stretches this year, defense was our strength, but I think we don’t really have that identity right now, so we’re searching.

“We’re playing small. We’re trying to play shooters — any way to score, because our scoring and our offense have been exposed in this series. And you’ve got to give the Knicks credit. I think that their switching has confused us, has taken away the movement that we ideally want to play with.”

The Celtics fully expected to have a size edge when they kept Kevin Garnett and Brandon Bass up front and started both Paul Pierce and Jeff Green, but that hasn’t translated well enough to the scoreboard.

“We’ve been tempted to try to exploit matchups that might not even be advantages,” said Ainge. “I mean, Jason Kidd can still play. I coached Jason Kidd when he was a three-time All-NBA player, and I don’t ever think it’s a mismatch when Jason Kidd’s guarding someone (Pierce, for example). I think at this stage of his career, he probably defends bigger guys much better than he defends quicker guys. I don’t think that’s a huge matchup advantage for us.