Joseph Randle put Dallas ahead early in the final period with a 1-yard scoring run, but Carmona gave the Raiders the lead for good four plays after the Cowboys fumbled a punt away at their own 9-yard line.
Tony Romo started for Dallas and completed 6-of-8 passes for 88 yards. He did not play in the Cowboys' exhibition opener last week against Miami.
Matt Flynn, favored to win the Oakland quarterback duel that has been ongoing during training camp, was 5-of-7 for 37 yards.
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