For Popovich, that was the question on the second night of a back-to-back. It took him almost all day to make up his mind, then 31/2 quarters of the Spurs' 95-83 loss to Portland to change it.

With 7:08 in the game and its outcome still somewhat in the balance, Popovich called Duncan to the bench for good.

"I didn't like the way he moved on a loose ball," Popovich said. "So I pulled him."

Duncan had just re-entered 32 seconds earlier, time enough for one offensive possession that ended with him clambering after a rogue rebound like a 32-year-old man on a pair of bad knees.

Popovich had seen enough. With Portland ahead 76-69 and surging, with his captain looking like he might topple at any moment, Popovich waved the white flag. Or, this being NBA Green Week, the green flag.

He did it to preserve Duncan, his most important star still remaining now that Manu Ginobili is out for the season.

"It's all got to do with his health, not standings or anything like that," Popovich said. "He felt good (at first). When I thought he didn't, that's when I decided to pull him."

The Trail Blazers, who had already come rushing back from a 19-point second-quarter deficit, were already firmly in control at that point. Duncan's untimely exit helped seal the deal.

With the victory, Portland's first in San Antonio since 2002, the Blazers forged a three-way tie with the Spurs and Houston for third in the Western Conference at 50-28.

Playing on bad knees for nearly two months, Duncan had been sitting the second nights of back-to-backs. Wednesday was his first such appearance since Feb. 11. That he was even out there to begin with surprised his teammates.

Duncan logged 23 minutes, 57 seconds Wednesday, after playing nearly 33 on Tuesday night in Oklahoma City. He scored four points, missed 6 of 8 shots and grabbed just five rebounds before Popovich sat him.

"Pop didn't want to play him at first," said Tony Parker, who scored 17 points. "He wanted to play. You have to admire Timmy for that."

Quick prediction: Popovich will not be so quick to relent Monday, when the Spurs finish their final back-to-back at Golden State.

Duncan didn't want to leave Wednesday's game. The way he stared at Popovich on his way to the sideline - half confused, half determined - said as much.

"I don't want a hero," Popovich told Duncan as he removed him from the game. "I want a healthy guy."

What the Spurs could have used most, less than 24 hours after a taxing victory in Oklahoma City, was an outcome that was also most improbable - a big, blowout victory over the second-youngest team in the NBA. For a while, it seemed doable.

The Spurs jumped out to a 19-point lead in less than 16 minutes. And by halftime, it was almost all gone.

By the third quarter, the Spurs were spent. LaMarcus Aldridge scored 14 of his 20 points in the frame as the Trail Blazers pulled ahead to take a 70-67 lead into the fourth.

"Given the makeup of our team, and you look at the makeup of their team, this late in the year, a back-to-back is going to be a whole lot tougher for us," Popovich said. "That showed as the game went along."

Nobody took the back-to-back harder than Duncan.

He was not available for comment after the game, but then again, what could he say that he hasn't already said?

Yes, his knees ache. They will be an issue for the rest of the season. All he can do is play on, for as long as his coach will let him.