ARLINGTON -- Felix Jones followed up a good preseason opener with another good performance, and quarterback Tony Romo noticed."I've never seen him more explosive or quicker than he has been in this camp," Romo said. "He also has taken it up a notch with his understanding of the game."Jones ran seven times for 56 yards against the Chargers. That gave him 10 carries for 79 yards in the preseason, a 7.9-yard average that looks more like the 8.9 average he posted as a rookie in 2008 than the 4.9 average he had the past two seasons combined.He also showed power against the Chargers. He kept churning through a tackle to gain 3 extra yards and a first down on an 11-yard carry. He also has carries of 22 and 18 yards in the preseason, and he said it was because he prepared well in the off-season."Definitely, during training camp you are learning things and keeping yourself in shape," Jones said. "I spent time in the weight room and stayed on top of things."Romo upset with INTThe first-team offense offered a mixed bag on three series, gaining 117 yards and scoring a touchdown on 20 plays.The starters went three-and-out on their first drive. Then, after the first unit picked up two first downs and crossing midfield on their second drive, Tony Romo threw an interception. Kevin Ogletree was double-covered on the play, and safety Eric Weddle had an easy pick.But Romo directed an 11-play, 80-yard drive ending in a 6-yard touchdown pass to Jason Witten. Romo rolled to his right to avoid the rush, and then threaded the ball between defenders Donald Butler and Steve Gregory."We were moving it on the drive when I threw the interception," said Romo, who went 8 of 12 for 58 yards with a touchdown and an interception. "That was disappointing because we had a good rhythm going, and we were in position to take that one down the field. It was good to come back on the next series. I just need to make sure I don't hurt our team with that interception. I'll look at the tape, learn from it and make sure that doesn't happen."So far this preseason, the first-team offense has gained 176 yards in four series and scored 10 points.Sensabaugh stands outEven though Gerald Sensabaugh tied for the team lead in interceptions last season with five, he was a free agent and not expected to re-sign with the Cowboys this season. But he is back as the starting strong safety.Sensabaugh not only showed up, but he stood out on the first-team defense, which allowed 152 yards on 27 plays Sunday night. He forced a fumble and had an interception overturned by replay."I feel like I came out here to play," Sensabaugh said. "I'm still learning the system. Last week I was only five days into the system, and this week I was able to play my game. I am getting the system down pretty good. I am trying to go out there and make a couple of plays. I should have had the interception, but it just shows what I can do."BrieflyDefensive end Marcus Spears was the only Cowboys player injured. Spears said he had a strained groin but he'll be back "real soon."The Cowboys were missing defensive end Jason Hatcher (toe), receiver Miles Austin (hamstring), linebacker Keith Brooking (hamstring), guard Montrae Holland (back), cornerback Mike Jenkins (stinger), cornerback Terence Newman (groin) and kicker David Buehler (hip), among others.Rookie Bill Nagy started at left guard. Rookie David Arkin started there last week. The Cowboys will continue to look at their options at left guard as long as Holland is out.Stephen McGee was unable to produce his fourth-quarter comeback magic this time. The Cowboys' third-string quarterback was 16 of 29 for 157 yards. He got the Cowboys to the 3-yard line in the final 2 minutes before throwing four consecutive incompletions.