Reasons for the Bulls' demise in their seventh straight road loss, this one 104-101 to the 76ers, were easier to determine.
The Bulls stormed back from a 13-point fourth-quarter deficit only to follow a familiar script on the final four possessions—poor defense, poor execution, poor decision-making.
After Ben Gordon's three-pointer with 36.7 seconds left tied the game at 101-101, veteran official Joey Crawford whistled Brad Miller for a borderline foul on Andre Iguodala with 22.1 seconds remaining. Iguodala, who scored 25 points, made the second of two free throws to break the tie.
Following a timeout, Samuel Dalembert blocked Derrick Rose's driving layup and Iguodala fired an outlet to a cherry-picking Thaddeus Young, who capped his career-high 31 points with a layup with 16.6 seconds left.
The Bulls were out of timeouts so Gordon dribbled upcourt and tried to pump-fake Willie Green into the air behind the three-point line, then leaned in and attempted a desperation three that rattled in and out.
"Hopefully, we can learn from this," Rose said.
The Bulls are now eight games below .500 for the first time since Jan. 28.
Rose led the Bulls with 20 points and played the entire fourth quarter as Del Negro rode a lineup of Rose, Kirk Hinrich, Brad Miller, John Salmons and Tim Thomas for all but the final 93 seconds.
Thomas, returning from missing four of five games with a hyperextended left knee, drained the second of his three three-pointers to cap a 13-2 run that tied the game at 88-88. The Bulls had fallen badly behind when the 76ers closed the third with a 15-2 run.
The nip-and-tuck game added to the undercurrent of emotion and electricity for the building's final game. Disco music blared—"It felt like Semi-Pro out there," Miller joked—and the sellout crowd of 17,563 was in full throat when Rose challenged Dalembert.
"It wasn't the play that we needed to run," Del Negro said. "They pressured the inbounds pass. We wanted to go high screen-and-roll, which was good for us. Derrick had an opening, thought he could score but we didn't convert."
Rose has been foiled more often than not on last-second attempts but said he isn't frustrated.
"Not at all," the rookie said. "I just missed a shot. I have many a game to hit shots like that."
The Bulls remained tied with the Bucks, but are only a half-game ahead of the Knicks, Nets and Bobcats.
"They're No. 1 in fast-break points, and we knew that going in, but we made turnovers and got them in the open court," Del Negro said. "That got us on our heels. We have to be more aggressive."