RENTON, Wash. - Darrell Bevell looked back at the tape of Seattle's preseason loss to Minnesota and it jumped out how difficult a night it was for new quarterback Tarvaris Jackson.

And perhaps how much Bevell was taking Jackson's knowledge of the playbook for granted, even if the rest of Seattle's offense is still learning Bevell's system.

"There were some hard plays for him in that game. We changed a little bit when Charlie (Whitehurst) went in there, gave him a little different stuff," Seattle's new offensive coordinator said Thursday. "... You kind of take it for granted (Jackson) knows the playbook so well, you kind of asked him to do some different things and we kind of simplified it after that. Maybe we could have helped him out there, or maybe I could have."

The lackluster effort from Seattle's starting offense through the first two preseason games has been the biggest concern among grumbling fans. The Seattle starters have yet to score, getting shut out in San Diego in two times on the field, then getting shut out in the first half against the Vikings last Saturday night.

Jackson realizes that points are hands down the biggest thing that the Seahawks need to see on Saturday night, when the first unit is expected to play into the third quarter at Denver.

"Last week, we got enough snaps to evaluate ourselves and we've got a lot of work to do," Jackson said. "We come out here every day, guys working, trying to get more on the same page, trying to communicate, make sure that we communicate clearly so we can be going the right direction so we can execute better. As we know on offense, if one guy does the wrong thing, it can kind of screw the whole play up."

Jackson understands why he's getting all the attention, especially considering the circumstances by which he came to Seattle. He's stepping in to replace Matt Hasselbeck, a 10-year starter in Seattle and the one who took the Seahawks to their only Super Bowl appearance.

But while most of the focus has been on Jackson's marginal numbers - 14 of 26 passing for 88 yards and one interception that was not his fault - the bigger issue is with Seattle's remodeled offensive line and its struggles protecting Jackson.

Jackson wasn't sacked last week against Minnesota. But he was running to safety for much of the first half as an offensive line that was without starting left tackle Russell Okung (ankle) and that features two rookies struggled with protection.

Bevell said some of that was by design on the play calls, but there was more pressure than he would like.

"We're still getting the feel for everybody," Bevell said. "Making sure that everybody is in the game at the same time is usually a big thing and we haven't been able to do that yet."

And that will continue this week in Denver. Okung will be out again and likely won't play until the season opener at San Francisco. Starting running back Marshawn Lynch will sit out with a sore ankle, while on defense middle linebacker David Hawthorne (knee) and strong safety Kam Chancellor (foot) will also be spectators.

With the exception of Okung, coach Pete Carroll indicated most would have likely played if this was the regular season.

Carroll also said the four players currently on the physically unable to perform list - receiver Deon Butler, defensive tackle Colin Cole, defensive back Roy Lewis and tight end Cameron Morrah - will likely not be ready for the start of the season. Anyone still on the PUP list when the regular season begins is not eligible to play for the first six weeks.

"They all have their own story, but right now we're just being real patient with that and don't expect those guys to make it by the first game at all," Carroll said.