SANTA CLARA, Calif. (AP) Long black hair swinging from his helmet, 303-pound defensive lineman Mike Purcell intercepted Dustin Vaughan's pass and returned it 37 yards for a touchdown to help the San Francisco 49ers beat the Dallas Cowboys 23-6 on Sunday night.

Purcell, a practice-squad player in 2013 and for all but the final two games last season, provided the highlight again after his six-tackle day in an Aug. 15 preseason opener loss at Houston.

Dallas quarterback Tony Romo's day was done after one three-and-out series then the Cowboys turned to Brandon Weeden, who left with a possible head injury.

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The Cowboys were expected to be cautious with Romo and Co. at Levi's Stadium, where the troublesome grass held up after causing concern for coach Jason Garrett and owner Jerry Jones.

Craig Dahl also added an interception for San Francisco against third-stringer Vaughan. Quinton Patton blocked a fourth-quarter punt by Tom Hornsey and scooped it up in the end zone for a 49ers touchdown.

Dallas avoided a shutout when fourth-string QB Jameill Showers threw an 8-yard touchdown pass to Nick Harwell in the waning moments.

Colin Kaepernick's targets are still finding their way.

Torrey Smith had the ball in his hands for a would-be 7-yard touchdown in the corner of the end zone before Corey White knocked it loose and had to settle for a 25-yard field goal by Phil Dawson.

Dawson added a 33-yarder to start the second quarter.

Smith, overthrown by Kaepernick in the first preseason game, will have to come through when the games count. He faces huge expectations as one of San Francisco's biggest acquisitions under general manager Trent Baalke. He signed a five-year contract that includes $22 million in guaranteed money and could be worth as much as $40 million.

Randy Gregory sacked Kaepernick for a 14-yard loss on the quarterback's second and final series. Kaepernick was 2 for 5 for 13 yards.

''That was the bright spot of the game. We were in some compromising positions on defense - bad field position and scoring opportunities for them,'' Cowboys coach Jason Garrett said. ''We kept them out of the end zone, had some timely sacks, and that was impressive.''

San Francisco linebacker NaVorro Bowman had three tackles in as many plays in his return for the first time since his devastating left knee injury in the NFC championship game in January 2014 at Seattle. He underwent surgery and missed all of last year recovering from tears in the anterior cruciate and medial collateral ligaments in his knee, and he had surgery to repair the ACL.

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