DEERFIELD, Ill. – Not too long ago, the Chicago Bulls owned the NBA’s stingiest defense. And then, the playoffs began.

A Bulls team that led the league in field-goal percentage defense during the regular season has allowed the Miami Heat to shoot 50.3 percent, and, no shocker, trails 2-0 as this first-round playoff series shifts to Chicago for Games 3 and 4 Thursday and Sunday.

“We didn’t come close to playing the type of basketball we need to play to win,” Bulls guard Kirk Hinrich said.

No one needs to remind the Bulls that recovering from a 2-0 deficit is a daunting task. But they saw that it could be done when the Washington Wizards beat them in six games in the first round last year.

Then again, the Wizards didn’t have two dominant forces like Shaquille O’Neal and Dwyane Wade or a veteran supporting cast like the Heat. And Washington didn’t reach the conference finals the previous year. The Heat have taken a 2-0 lead on five other occasions and have not lost.

“We know if we get this game on (Thursday) that it’ll be hard for them to come back,” O’Neal said. “That’s what we want to try to do. We want to fly up there and take care of business (Thursday) night.”

They’ve been playing like they mean it, although the Bulls haven’t gone quietly.

Miami won Game 1 by five, then held off a late charge by Chicago in a 115-108 victory on Monday. And while O’Neal and Wade have performed as expected, the supporting cast has given the Bulls fits.

Jason Williams is averaging 19.5 points in the series. Antoine Walker is contributing 13.5 points and 7.5 rebounds. And James Posey has gone 6-of-12 on 3-pointers.

“If Antoine and Jason and Posey are going to keep shooting like that, I’m going to keep looking for them,” said O’Neal, averaging 24.5 points and 11.5 rebounds.

Chicago coach Scott Skiles thinks Tyson Chandler has done as good a job as he can on O’Neal.

The problem is the reaction that occurs when O’Neal gets the ball in the post. The defense collapses, and the big man passes the ball. His teammates either hit the shot, blow by the Bulls or pass back to O’Neal for an easy basket.

“We’ve got to do a better job with that chain of events,” said Skiles, whose team held opponents to .426 shooting during the regular season.

That means better closeouts by the perimeter defenders, stopping the penetration.

“We’re just running by people,” Hinrich said.

Defense isn’t the only issue.

The Bulls committed 19 turnovers in Game 2 – the sloppy kind. They dribbled into traffic, got stripped of the ball and that put more pressure on the defense.

Another issue: Ben Gordon.

After scoring 35 points in Game 1, he finished with 13 on 5-for-16 shooting on Monday. Then, he bemoaned a game plan that he said limited his involvement in the offense.

Skiles took issue, saying the Bulls “constantly” run plays for Gordon.

“I made it very clear to him what my view was,” Skiles said. “We have more plays in our offense (for Ben) than any team has in their offense for any player in the league.”

Skiles said he has “heard similar things” throughout the year but added, “It’s something he’s going to have to get over. He has to face the personal responsibility of what he needs to get done.”

Gordon called it a “misunderstanding.”

“I was asked a specific question,” he said. “‘Why are you standing in the corner, not being aggressive (and) trying to get the ball?’ I was trying to answer it the best I could. I didn’t mean (harm) in any way.”

The biggest concern for the Bulls is the defense.

Skiles estimated O’Neal scored four baskets “on his own” on Monday. The rest came from penetrations and lobs.

And Wade, like O’Neal, has found open teammates when the defense collapses on him.

“They’re a team that helps a lot, so you’ve got to get off the ball and trust your teammates. … As long as guys continue to make shots and Shaq keeps passing the ball out the way he has, we’ll be fine,” said Wade, averaging 25.5 points while shooting 43.9 percent.

Notes: Heat coach Pat Riley missed Wednesday’s practice to attend his mother’s funeral in upstate New York. … Center Alonzo Mourning is questionable with a torn calf muscle -ÿan injury he sustained in an 82-73 loss at Detroit on March 22. … Skiles expects Bulls F Malik Allen, bothered by back spasms, to be available for Game 3.