SAN ANTONIO – Brent Barry blamed himself and his fellow Spur guards for failing to get Tim Duncan the ball in the fourth quarter of Tuesday night’s disastrous Game 6 loss to the Pistons.

Barry vows it will change tonight in Game 7, when the Spurs and Pistons slug it out for the NBA championship. Duncan has been “Tiny Tim” since Game 3, especially dreadful from the free-throw line.

In Game 6, he took just 14 shots, and went without a field goal for a 12-minute stretch of the fourth.

“With Rasheed [Wallace] on the bench and their smaller lineup, we could’ve taken advantage of Tim on the block more,” Barry said. “The ball didn’t go into him. I take that responsibility as a guard. Tony [Parker] does, Manu [Ginobili] does. We did not put Tim in situations where he could’ve been a lot more effective for us.”

Duncan has never played a Game 7. The Spurs will need a monster effort from him tonight to thwart the defending champs, who smell blood.

“Tim beats himself up over the fact we lost the game,” Barry said. “He can’t beat himself up over the fact we didn’t get him the ball when we should’ve. We have to get him the ball.”

Barry was trying to take the heat off Duncan, who’s averaging just 19.8 points in the six games and shooting a Shaq-like 64.6 percent from the free-throw line. It only seems all his free-throw bricks have come in the fourth quarter.

“We haven’t run the sets where we’re looking for Tim specifically,” Barry said.

Said Duncan: “I want to get the ball, I want to be effective more than anything, and how do you balance that?” Duncan said. “I don’t know.”

He’d better figure it out.