PORTLAND, Ore. - The 76ers stood toe-to-toe with the NBA's hottest team for three quarters tonight, then abruptly fell flat on their faces in a free-falling fourth period.

Leading by 63-62 entering the final quarter, the Sixers surrendered the first 18 points of the period on the way to a 97-72 loss before a sellout crowd of 20,464 at the Rose Garden. The Blazers outscored the visitors, 35-9, in the fourth quarter.

The Sixers (13-17) ended a modest three-game winning streak. Meanwhile, Portland (18-12) has a real winning streak, now 13 games, the most in the NBA this season.

Afterward, Sixers coach Maurice Cheeks insisted that his team did not collapse in the fourth quarter, although it's hard to think otherwise after they shot 4 for 19, failed to attempt a free throw, and committed seven turnovers. Portland hit 14 of 19 shots (73.7 percent) in the final period.

"Their defense was good; our offense was not good," Cheeks said. "I'm not going to attribute it to us losing our composure or collapsing."

They certainly did not display a lot of poise.

The Sixers were so frustrated by the fourth-quarter meltdown that Cheeks earned a technical foul, along with guards Lou Williams and Andre Miller and center Samuel Dalembert.

"I don't think we did enough," said Andre Iguodala, who scored a game-high 24 points. "We could have done a little more, get loose balls, play hard. We got a little frustrated by calls. Whether they were right or wrong, that affected us."

Where's Gordan Giricek when you need him?

The newly acquired Sixer could not play because the trade for Kyle Korver was not officially completed an hour before tip-off. (The results of physicals for both players had not been approved by then.)

Then again, it's doubtful Giricek, Korver or anybody else could have stopped the fourth-quarter barrage.

Portland actually figured that turnabout was fair play. On Nov. 16, the Blazers blew a 25-point lead in a 92-88 loss to the Sixers in Philadelphia.

Tonight, it was the Sixers who squandered a double-figure advantage. They led by as many as 11 points in the third quarter.

The Blazers could sense that the Sixers were dragging. Like all good teams, they went for the jugular.

"They were driving, and we were stopping them and they weren't getting back on defense," said Blazers guard Brandon Roy, who scored 22 points. "We said they were putting their heads down and said we have to keep hammering this team, because they came back on us last time, and we didn't want to let up this time."

Then Roy said something that might have been the most damning.

"We definitely saw them kind of folding a little bit," he said.

During the winning streak, Roy has averaged close to 23 points. While he hurt the Sixers, reserves Travis Outlaw, James Jones and Jarrett Jack combined to score 27 of Portland's 35 fourth-quarter points.

Nothing the Sixers did seemed to work. All game, their half-court offense struggled. The only thing that kept the Sixers in the game was that the Blazers were missing open shots. Portland shot 38.6 percent from the field in the first three quarters.

Then came the fourth quarter, when the Blazers couldn't miss and all the Sixers could do was watch in agony.

From the Sixers' perspective, the only positive is that they do not have long to dwell on this loss because of Monday's New Year's Eve special in Seattle.

"There is only one positive thing we can look to," Williams said. "We have another game so soon and get a chance to redeem ourselves."

Contact staff writer Marc Narducci at 856-779-3225 or mnarducci@phillynews.com. Read his blog at http://go.philly.com/deepsixer.