CHICAGO - Welcome back.

After a feel-good three weeks, it felt just like old times on Tuesday night inside the United Center.

The 76ers looked like the Chicago Bulls' junior varsity squad.

The Bulls led by 18 points at halftime and then continued dismantling the Sixers, winning by 121-76.

In the third quarter, the Bulls led by as many as 41 points, and the 21,521 in attendance - a sellout - were amusing themselves in ways other than watching the game.

Like leaving the game. Or chanting for seldom-used forward Brian Scalabrine.

In the fourth quarter, Chicago's lead reached 51 points.

The Sixers, who will play at Boston on Wednesday, dropped to 11-17. The Bulls, led by Derrick Rose's 22 points and 12 assists, improved to 17-9.

"We would go out of time-outs and we were just looking around," said Sixers coach Doug Collins. "I could just tell. It was one of those nights. When you've been around 40 years, you just after a while feel like there's no reason to say a whole lot."

Entering Tuesday's game, the Sixers had won eight of their previous 11 games.

So which was the anomaly: Tuesday's complete collapse or the previous three weeks?

"If you ask me, I think it's the last 10 games," said Sixers swingman Andre Iguodala, who scored a team-high 17 points. "We've just been getting by. We've been getting some good wins at home, but I don't think we've been playing good basketball. Other teams haven't been playing too well against us and then we start winning, teams wake up. They don't sleep on you anymore."

No one thought a victory in Chicago would be an easy accomplishment, but the extent of the embarrassment seemed surprising as well.

The Bulls went through the Sixers like a knife through snow: clean and easy.

Chicago shot 61.9 percent in the first quarter, 61.1 percent in the second, 70 percent in the third, and 64.7 percent in the fourth.

Scalabrine checked into the game with 5 minutes, 41 seconds remaining and received a partial standing ovation. He scored with 3:59 left to give Chicago its largest lead, 118-67, and those remaining exploded from their seats. Afterward, many grabbed their coats and walked up the aisles, having checked the final box on their night's checklist.

"I just told them, I said, 'Guys, we've worked too hard. I hope that's not what we want to become. I'll give you one night,' " Collins said of his postgame speech.

Before Tuesday's game, Collins had a clear number in his mind: 45 percent. That was the shooting percentage he needed his team to keep Chicago below. Given his team's less-than potent offense - it struggles to reach even 100 points - Collins needed his team to use its usually energetic defense to keep the game close.

Oops.

Iguodala explained the team's postgame discussion: "We have another one [Wednesday] against an even better team. You want another ass whupping or do you want to compete and try to get a win before the break? It's up to us."

Contact staff writer Kate Fagan at 856-779-3844 or kfagan@phillynews.com.