SAN FRANCISCO — A new season looked awfully familiar Sunday. With an emphasis on awfully. The San Francisco 49ers committed five turnovers, three of them by newly anointed quarterback J.T. O'Sullivan.

And the defense could do nothing to stop the ball-hogging Arizona Cardinals, who unleashed play after frustrating play en route to a 23-13 victory at Candlestick Park.

"It's hard to have production offensively when you're hardly on the field," 49ers receiver Bryant Johnson said.

Arizona ran an astounding 45 offensive plays in the second half while the 49ers ran just 15.

That's how the excitement of a capacity crowd on opening-day dissolved into scattered boos by the final seconds.

New era, same errors.

"The percentage of winning goes down with each turnover. You can say it starts and stops with that," said O'Sullivan, who was 14 of 20 for 195 yards in his first NFL start.

49ers Coach Mike Nolan, whose hot seat was turned up a few degrees, also pointed to the damage inflicted by the "six turnovers." (There were four lost fumbles and an interception).

Whatever the count, the result was painful. The 49ers couldn't hold onto the ball and the Cardinals refused to let it go.

The Cardinals' time of possession edge in the second half was 22:28 to 7:22.

Arizona's game of keep-away included one drive of 15 plays (80 yards) and another of 18 plays (62 yards). Both drives came with the 49ers trailing by a touchdown and desperately trying to get the ball back.

"What disappoints me," Nolan said, "is that as a defense, we need to play a 60-minute game where whenever we're called upon to stop them, we need to do that."

Tied at halftime, the Cardinals took a 13-10 lead on Neil Rackers' 31-yard field goal midway through the third quarter.

Arizona pushed the advantage to 20-10 later in the quarter when running back Tim Hightower pounded into the end zone on fourth-and-one from the 49ers' 2.

The 49ers' comeback hopes, meanwhile, never got off the ground. They had three second-half drives: field goal, fumble, end of game.

After Rackers' go-ahead field goal, for example, Takeo Spikes muffed the kickoff return. Spikes, a linebacker, was on the special-teams unit as a blocker, but the ball came his direction at the 49ers 33. The Cardinals' Matt Ware recovered and, eight plays later, Hightower pushed in the pivotal touchdown.

Nolan said Spikes generally has good hands — a requirement for special-teams blockers. He noted that Kentwan Balmer, normally a defensive end, was put in the same situation Sunday and managed a 6-yard return.

Asked to pinpoint the problem with fumbles, Nolan was blunt.

"Carelessness in carrying the ball is what I think it is," he said.

The culprits included O'Sullivan, who was sacked and fumbled on the first offensive play after the final two-minute warning. He had also fumbled when hit midway through the first quarter.

The Cardinals, in contrast, had a turnover-free day — which helps explain why Arizona was the only NFC West team to win on opening weekend.

"Any time you lose the turnover battle, you're going to lose the game," said Cardinals running back Edgerrin James, who had 100 yards on 26 carries.

Other than the turnovers, O'Sullivan showed a spark at times. He made plays under pressure, including some nice dump-off passes to Gore and Vernon Davis as he was being hit.

But not every improvisation turned out well. On a third-down play in the first quarter, O'Sullivan's pre-snap read told him to get the ball to Isaac Bruce.

When Bruce was covered well, O'Sullivan's eyes found Arnaz Battle over the middle of the field. But throwing late over the middle is a dangerous play, and safety Adrian Wilson swooped in for an interception.

"I moved to my left and just saw Arnaz coming open," O'Sullivan said. "When I threw it, I thought I had it."

The 49ers' lone touchdown came when running back Frank Gore bolted 41 yards in the first quarter, providing a 7-3 lead. Gore finished with 96 rushing yards on 14 carries and 55 yards on five catches.

Imagine what he could have done if the 49ers had actually managed to hold on to the ball — or stop the Cardinals offense.

"A lot of mistakes and we came out flat," Gore said. "We beat ourselves."