Baltimore's offensive line entered the year billed as perhaps the team's top unit.

All five starters from last year's dominant group returned, and the Ravens have some of their best depth at the position.

Sunday's game in Denver, however, didn't match the hype.

The Ravens never got the ground game going with any consistency. Joe Flacco took just two sacks, but was pressured on a whopping 64 percent (22 of 34) of his drop backs, according to Pro Football Focus (PFF). That limited the ability to attack downfield and complete even short passes.

Baltimore's offensive line almost collectively got low marks by PFF. Right tackle Rick Wagner had the worst rating (negative-10.4), followed by James Hurst (negative-10.1), left guard Kelechi Osemele (negative-4.1)* *and center Jeremy Zuttah (negative-1.9). Pro Bowl right guard Marshal Yanda got the best grade of any offensive player (plus-2.4).

"It was just on the edges," Flacco said. "Even late down the stretch there, I probably had another shot at Steve [Smith Sr.] if I don't get batted or hit my shoulder or something happens like that."

There are a few factors that contributed to the offensive line's tough day.

They put themselves in difficult pass protection situations by not getting the rushing attack started. They lost their starting left tackle during the first series.  They went up against a very talented Broncos pass rush. They have missed a lot of time together in the preseason.

The first problem for the offensive line was an inability to clear enough holes in the running game. Baltimore ran 23 times for 73 yards, an average of just 3.2 yards per carry. The Ravens especially had trouble on first down. They ran eight times on first down for just seven total yards. They were stopped for no gain on six of those runs and stopped in the backfield on one.

Part of the problem may have been that Denver Head Coach Gary Kubiak knows exactly how to stop his own run scheme. The Ravens run the same scheme Kubiak installed in Baltimore last season.

"They had a pretty good game plan," Osemele said. "They have a talented defense. They had an extra hat on some of the zone plays, the slants, the penetrating things like that. It felt like they had a good idea of what we were going to do."

With Baltimore in too many second-and-long and third-and-long situations, Denver's pass rushers could devote themselves to getting after Flacco. That's not good considering Denver's Von Miller and DeMarcus Ware are one of the NFL's best duos. They share 11 Pro Bowls between them. Miller and Ware were getting excellent explosion off the ball, making things tough on the tackles.

"We had some situations where we had to throw the ball," Wagner said. "It's never easy to go against those kind of elite rushers."

Head Coach John Harbaugh said the Broncos didn't bring any blitzes or special pressure that his team hadn't practiced for. It was more just Miller and Ware winning on the outside with speed and speed-to-power rushes.

"Our tackles, they've got to do a better job," Harbaugh said. "They've got to set square and they've got to punch on time. When they do that, they'll do well against anybody. When you don't do that, you're not going to do well against anybody. That was an issue for us over the course of the game."

Harbaugh did say that the coaches could have done a better job helping the tackles once it was clear that they were having major problems. Baltimore had plans to use extra blockers, such as running backs or a fullback, to help chip rushers.

"We didn't get to [those plans] as much as we should have," Harbaugh said. "We should have gotten to those a little more often and slowed that rush down."

The Ravens perhaps could have contained those outside rushes better had starting left tackle Eugene Monroe been out there. Monroe suffered a concussion on the first series of the game, leaving James Hurst filling in as he did so often last season. Hurst started seven games for Monroe last year, but it was still a difficult assignment for the former undrafted player.

Injuries have been a problem for the Ravens* *offensive line already this season, which also may have contributed to the slow start. Monroe missed the third preseason game and practice time due to a wrist injury. Osemele only played in the first preseason game due to an Achilles problem.

"First-game jitters, emotions all over the place. It just took us a while to get things under control and play with technique and play as a unit," Osemele said. "I didn't play in many preseason games and we just had guys that were banged up through camp. I think as the season progresses, we'll start faster."

While it was a tough opener, the Ravens still have a lot of time to turn things around. Baltimore gave up three sacks in last year's season-opening loss against the Bengals. The Ravens plugged away and finished the year with one of the best offensive lines in football.

"This is just game one of many [games] to come," Wagner said. "We've got a whole season ahead of us. I think, as a group, last year we just kept getting better and better. This year, I think the same thing will happen."