DEERFIELD, ILL. ? They played six tense games in the first round of the playoffs last year, and their recent history includes hard fouls and harsh words.

But if there’s a rivalry between the Miami Heat and Chicago Bulls, that’s news to Shaquille O’Neal.

“They want to make it a rivalry,” the Heat center said. “If I’m walking down the street and you say to me, ‘We’re rivals,’ we’re not rivals,” he said. “You have to do something to me for us to become rivals. It’s not a rivalry. You have to do something before it’s a rivalry.”

The Heat have a championship to defend. The Bulls have higher expectations after consecutive opening-round exits.

And here they are, standing in each other’s way again with another first-round series set to begin today in the United Center – two rivals ready to go at it. Or are they rivals?

“I don’t know,” Bulls coach Scott Skiles said. “I’m not even sure what that means. I know it’s fun to talk about, but I guess I believe a rivalry means some team’s won the title once or twice and another team’s won it once or twice. They knock heads over and over again in the finals. First-round opponents? I don’t know.”

The tension between the Bulls and Heat dates back at least two years, picked up during the playoffs last spring and continued this season.

Chicago’s Andres Nocioni got called for a flagrant foul on Dwyane Wade and pushed him, and the Heat’s Udonis Haslem got ejected after coming to Wade’s defense April 5, 2005.

In Game 3 last season, Miami’s James Posey knocked down Kirk Hinrich in the open court, resulting in an ejection and one-game suspension. The Bulls called it a cheap shot. Posey said Hinrich didn’t see him. And Miami coach Pat Riley said afterward: “Maybe something happened at the other end, but I don’t like that. There’s got to be some dignity in the game.”

The Bulls won Games 3 and 4 and were leading in the third quarter in Game 5 before Miami rallied.

This season?

The Heat got their championship rings and saw the banner raised before the Bulls routed them in the season opener, 108-66. Chicago rookie Tyrus Thomas got a painful introduction to the NBA, suffering a broken nose while going for a rebound against Posey.

There was more drama when Chicago beat Miami 109-103 in December in the United Center. This time, Wade left with a sprained wrist after Hinrich tugged at his arm midway through the first quarter. And Posey got ejected again when he took down Luol Deng from behind in the fourth quarter.

Bad blood?

“As far as I’m concerned, it’s just competitiveness,” Hinrich said.

Hinrich found himself in a mini-storm this week after he was quoted as saying, “We should’ve won last year’s series, honestly. We felt we should’ve won Game 5. So we’re confident.”

The Heat took exception, and Hinrich didn’t understand why.

Wade said, “They wanted us. They wanted this opportunity. Here it goes.”

For the Bulls, it’s a big opportunity.

They made a splash in the offseason when they lured four-time defensive player of the year Ben Wallace away from Detroit with a four-year, $60 million contract, and they did it with the idea of advancing past the first round. They expected to contend in the Eastern Conference, and had control of the second seed until losing to New Jersey in the season finale.

That dropped them to the fifth seed and into a first-round matchup with the Heat.