OAKLAND -- The Dallas Cowboys' defense ended the Oakland Raiders' first offensive possession with an interception and their last one with another in a 3-0 win in the preseason opener Monday night.

A field goal was all the Cowboys would need to beat the Raiders in a lackluster effort from both units at O.co Coliseum.

What it means: The first-team offense has some issues. We still don't know who the No. 3 wide receiver is going to be and if the interior of the offensive line will improve. It was good to see defensive end Marcus Spears (three tackles), safety Gerald Sensabaugh (interception) and Dez Bryant (24-yard reception) play well.

First-team offense: The first-team offense didn't have starters Miles Austin, Nate Livings and Phil Costa, but Bryant, DeMarco Murray and Tony Romo were on the field. But the Cowboys' first unit came up with a grand total of zero points in three possessions. Romo hit Bryant with a pass for a first down, but a sack -- thanks to a missed block by center David Arkin -- and a dropped pass on a screen to Felix Jones hurt the drive. The third and final possession resulted in Jason Witten catching an 8-yard pass that was one yard short of the first-down marker.

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"I think we need to eliminate some of the mistakes that put us in a hole tonight," Romo said at halftime. "We have a lot of young guys playing right now and we are just going to be able to evaluate this tape and get better from it. Right now is a time for us to correct the mistakes that are on the tape. I think the effort was there tonight, we just need to have better execution -- and we will."

Arkin plays well: With Costa out, Arkin got the start at center and didn't fumble any snaps, but he was called for one penalty and may have caused a sack. The key for Arkin was technique and playing with confidence. He seemed to do that at times Monday, but the run game didn't get going with Murray and Jones. Arkin played the bulk of the game at center, up until about six and half minutes remained, and then Harland Gunn took over.

Spears shows up: Spears is fighting for a roster spot and came up big with three tackles on the night. He had a better night than fellow defensive ends Sean Lissemore and Kenyon Coleman. It's early in the preseason, but Spears needed to make some plays here to prove his value to the club.

Who surprised us?: A couple of days ago, Jason Garrett snuck in a comment about how well rookie defensive tackle Ben Bass was looking in training camp. On Monday night, Bass had two sacks -- both while chasing Oakland's Terrelle Pryor -- and a key tackle for loss on a third down that pushed the Raiders back for a longer field-goal attempt. The tackle led to a 36-yard missed field goal by Eddy Carmona.

Who didn't?: Bryant played in the preseason opener despite suffering some tightness in his hamstring during Saturday's practice. He was a game-time decision but looked good in pregame warmups, hopping around and running with a burst. He finished with one catch for 24 yards.

Bonus notes: All three quarterbacks played in the game, with Rudy Carpenter finishing up. ... Sensabaugh showed some play-making skills with a first quarter interception. ... On one sequence, the special teams unit was called for three penalties. ... The replacement officials showed an amazing ability to throw flags. We saw two thrown about 20 yards. They also placed a ball on the infield dirt, away from the hash marks. Romo had to stop play to point it out. ... The Raiders misses two field goals. ... Safety Mana Silva picked off a Pryor pass to end the Raiders' last possession of the night.

Who's next?: The Cowboys will visit the San Diego Chargers on Saturday night for their second preseason game.