PHOENIX (AP) – Awesome offense, dreadful defense.

Deserved or not, that’s the image of the Phoenix Suns, a perception magnified by their fourth-quarter flameout against the San Antonio Spurs on Sunday in Game 1 of the Western Conference finals.

The Suns were buried in an avalanche of 3-pointers, layups and hook shots by Tim Duncan in a 43-point final quarter that lifted the Spurs to a 121-114 victory.

“They scored that much in the fourth quarter?” the Suns’ Shawn Marion said. “Man, we didn’t play no defense. Anybody can win a game if you let them score 43 points in the quarter.”

The 43 points matched a Spurs’ playoff record and fell just two shy of a record for a Suns opponent in the postseason, a mark set against the “Showtime” era Los Angeles Lakers in 1985.

“We weren’t expecting a team to go on a run like that,” Amare Stoudemire said. “We’re normally the team that goes on the fourth-quarter runs. We’ve got to step it up defensively, especially in the fourth quarter. We’ve all got to play hard. We’ve got to play 100 percent out there.”

The Suns don’t need great defense to win. They do, however, need at least a few stops when the game is on the line. Phoenix led 82-78 after three, then the Spurs shot 73 percent in the fourth quarter (16-for-22).

Playing less than 48 hours after wrapping up their conference semifinal series with an overtime victory at Dallas, the Suns lacked their trademark energy, especially while San Antonio pulled away in the final five minutes.

“I just think that we kind of let fatigue affect us mentally,” Steve Nash said. “I think we lost our concentration. I think we lost our fight in just enough stretches to lose the game. I thought when things got hard, we just didn’t dig deep enough.”

Phoenix coach Mike D’Antoni always has scoffed at the idea that his depth-shy team could be worn down, and wasn’t about to change his mind on Sunday.

“We’re not tired,” he said. “It’s a matter of concentration and pushing yourself over because there’s no one out there later that we have to carry off the floor. That’s what we have to give to a point of exhaustion. We have to do that.”

The biggest defensive breakdowns came when the Suns, who had guarded Duncan one-on-one most of the game, switched to a double-team, leaving Brent Barry open for consecutive 3-pointers that turned a 100-98 lead to a 106-98 advantage with four minutes to play.

Even when the Suns had a rare defensive stop down the stretch, San Antonio usually got the ball again. Of the six missed shots the Spurs had in the fourth quarter, they grabbed the offensive rebound four times.

“It always comes down to about five or six plays. I just didn’t think we competed hard enough on those plays,” D’Antoni said. “You are not going to beat a team like San Antonio unless you do.”

Phoenix’s problems were exacerbated by Marion’s bad offensive outing. After scoring 38 in Dallas on Friday night, he made 1 of 6 shots for three points on Sunday.

“I’ve got to find a way to get involved,” Marion said. “I had more rebounds than shots, and that’s not good.”

In order for me to help this team, I’ve got to get involved more.”

The abrupt loss of homecourt advantage should be a jolt to his team, Nash said.

“It was a tough situation,” he said, “but these are situations that we have to learn our lessons through, and realize what it does take to make the difference between being a contender and a champion.”