Mike Celizic

It has to be agonizing to be a Celtics fan right now. You’re watching a team that gets introduced as the defending champs, but it doesn’t play that way. And unless the tendon fairy shows up and magically heals Kevin Garnett’s knee, there’s no way they will.

They’re playing hard, fighting for rebounds, diving for loose balls, hustling on defense, pushing the tempo, and it’s all they can do to keep up with the Chicago Bulls. The Celts took a 3-2 first-round series lead in yet another overtime game — the third in five games. They should be able to win one more game against a team that won just 41 of 82 this season, but it’s hardly a sure thing.

There has been exactly one easy win in this series — the Celtics’ 107-86 victory in Game 3. The rest have been like Tuesday night’s Game 5 — steel-cage death matches disguised as basketball games.

And this is against the seventh seed in the Eastern Conference. It’s impossible to envision this team beating top-seeded Cleveland. It’s hard to see them surviving another round to even play LeBron James and the Cavaliers.

Of course, it looked that way last year, too, when the Celtics needed seven games to beat the eighth-seeded Hawks in the first round and had trouble throughout the playoffs winning away from home. It wasn’t until the finals against the Lakers that they finally played like the champions they were.

It would be beyond impossibly optimistic to hope that the Celtics can do again this year what they did last. Without Garnett, they’re just not good enough to give games away.

That said, it’s too easy to blame this year’s struggles on the loss of Garnett. He was one of the Big Three, which means there’s still a Big Two on the court. But Ray Allen and Paul Pierce have not taken this series over as great players should.

In Game 5, Allen fouled out with more than four minutes to play in regulation, a nearly unforgivable breach of veteran discipline. When he trudged to the bench, he took a mere 10 points with him. Once there, he joined teammates who spent much of the game staring glumly at a game they couldn’t take control of.

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Pierce did make himself heard, but he waited long enough to do it. After the Bulls had gone up by 10 in the fourth quarter, Pierce started to contribute, and his scoring down the stretch and in overtime was the difference in the game. Other huge contributions came from center Kendrick Perkins, who pulled down 19 rebounds, and power forward Glenn Davis, who’s played consistently well and had 21 points Tuesday.

But the man who’s keeping the Celtics together is third-year point guard Rajon Rondo, who led the Celtics with 28 points on 12-of-22 shooting. Rondo averaged just 11.9 points during the regular season, but he’s averaging more than 24 in the playoffs and nearly a triple double to boot.

Rondo was a guy whose outside shooting was supposed to be a weakness, but he has been nothing short of brilliant in this series. Add in just over 10 assists per game and you have an All-Star performer.

So the Celtics really do have three great players on the court — Pierce, Allen and Rondo. It shouldn’t be this hard to beat the youthful Bulls, not with that core. But it is.

The Celtics are cutting things way too close. They won Game 5 as much because of the Bulls’ youth and inexperience as because of Pierce’s clutch shooting. Chicago has to be kicking itself after Tuesday’s loss. They blew a big fourth-quarter lead, took too many bad shots and had too many critical turnovers and lost a game that could have put them in a commanding position. There’s no nice way to say it: The Bulls choked.

That inconsistent play will probably be what decides this series. As well as rookie point guard Derrick Rose has played, his inexperience has showed at critical times. As a team, the Bulls have been the gang that can’t shoot consistently. Their field-goal percentage has ranged from a high of .500 to a low of .375. In Game 5, they shot just .400, and that’s not going to get it done.

Thanks to the shortcomings of both teams, it’s been a terrific series to watch — at least for a fan who has no rooting interest. For Celtics fans, it’s got to be sheer torture.

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