No surprise: Rams' offense a work in progress in loss to Raiders

That the St. Louis Rams only posted a field goal in their 18-3 loss to the Oakland Raiders in the preseason opener should come as no surprise. It's a group that's going to take some time to coalesce and expecting it to happen in just a couple of weeks of practice and one preseason game is a fool's errand.

Whether it was the starters or any of the backups, the Rams simply couldn't muster much offense, even against the team they beat 52-0 in the 2014 regular season. The Rams finished with 285 total yards and, aside from their opening drive, didn't come that close to reaching the end zone.

Some more quick thoughts on the preseason opener:

QB depth chart: As expected, Nick Foles made the start and played two series, but there's no doubt it's his job. The real battle at quarterback is for the No. 2 job, where Case Keenum got the first opportunity ahead of Austin Davis. Keenum played the second and third quarter, performing better in the third. He stood and delivered well in the face of pressure a couple of times on a third-quarter drive and went 12-of-17 for 83 yards on the night. Davis got the third opportunity, going 1-of-2 for 12 yards before giving way to rookie Sean Mannion. Safe to say, neither Davis nor Keenum did much to separate from each other.

Maybe that dude could start: It's strange to say about a former No. 8 overall pick, but Tavon Austin offered a glimpse of his game-breaking ability on a 35-yard catch and run on the opening series. He isn't expected to be a starter in a technical sense, but he reminded why he needs to be heavily involved in the offense because he brings something unique to the table.

Who got hurt?: It's become an all too familiar refrain, but the Rams were only four plays into their opening drive when left guard Rodger Saffold left the field holding his right arm. He did not return to the game. Linebacker Daren Bates also limped off in the second quarter with a knee injury and did not return.

Among those not playing because of previous issues: running back Todd Gurley, end Chris Long, receiver Brian Quick, cornerback Brandon McGee, cornerback E.J. Gaines, linebacker Korey Toomer, guard Cody Wichmann, tight end Brad Smelley, defensive tackle Doug Worthington and end Eugene Sims.

Surprise performer: Undrafted rookie cornerback Imoan Claiborne has made a habit of coming up with interceptions in practice and carried it over to Friday's game. He picked off Christian Ponder to end the first half and continues building a case to steal a roster spot at a crowded position.

Rookie watch: Right tackle Rob Havenstein and right guard Jamon Brown started and played the first two series with the starters before calling it a night. They did well to create room for back Benny Cunningham to move the chains on a third-down run and had no serious issues in pass protection though Havenstein appeared to have a couple of hiccups. Andrew Donnal, who came in at right tackle with the second-team offense, picked up a holding penalty to negate a big gain.

When it was starters vs. starters, the Rams looked ... : Alternately good and bad. Perhaps as you'd expect from a preseason opener, the Rams' starters played all but one play of the first quarter and had to take the good with the bad. With starters on the field, the Rams and Raiders were tied at 3.

Foles completed his first two passes for 61 yards to set up a field goal but went nowhere on the second drive, completing one of his next three passes for 8 yards and taking two hits and a sack.

On defense, the vanilla Rams had some trouble with Oakland's misdirection in the run game and Derek Carr's quick release in the passing game. Cornerback Trumaine Johnson, who picked up a 15-yard penalty for grabbing a face mask, redeemed himself by jumping a slant at the goal line for an interception to kill the Raiders' second drive.

One reason to freak out: Although initial returns are that Saffold's shoulder issue isn't serious, the Rams can't afford to lose him for an extended period. He's the only offensive line starter with more than 12 games of playing experience. Brandon Washington replaced him at left guard and gave up a sack with Foles still in the game. The Rams simply don't have much proven depth behind the starters on the offensive line.

Man in the middle: The Rams listed Barrett Jones as the starting center on their "unofficial" depth chart this week but it was Tim Barnes getting the start and playing the first two series. Jones came in with the second team and Demetrius Rhaney came in later. That trio is, of course, competing for the starting job in the middle, but the Rams don't plan to make a decision right away. For what it's worth, Barnes held up pretty well.

Penalty woes remain: Last week, Rams coach Jeff Fisher said he was pleased with his team's emphasis on cutting down on penalties. That didn't last long. They struggled again against the Raiders, posting 10 accepted penalties for 75 yards with at least three more infractions that were declined. Each preseason, Fisher says it's a problem his team is working to correct. And each year, it carries over as the Rams have the most penalties and penalty yards in the NFL in Fisher's three seasons in St. Louis.