Kansas City Chiefs quarterback Matt Cassel throws against the Minnesota Vikings in this Aug. 21 file photo from Minneapolis. It’s still unknown whether Cassel (knee injury) will start K.C.’s opener on Sunday at Baltimore.

Kansas City, Mo. ? Forty-eight hours before the Kansas City Chiefs launch their season in Baltimore, coach Todd Haley indicated he may have several positions besides quarterback where the starters were not set in stone.

Matt Cassel, still wearing a knee brace, worked again at practice Friday. But Haley said whether Cassel would face the rugged Baltimore defense would probably be a game-time decision. The first-year head coach also said it was still uncertain whether Brodie Croyle or Tyler Thigpen would start at quarterback ahead of Cassel, who injured his left knee on Aug. 29 and did not return to practice until Monday.

Cassel was listed as questionable on Friday’s injury report, along with wide receiver Terrance Copper and cornerback Brandon Flowers.

Haley hinted there may be other positions whose starters would not be decided until Friday afternoon’s staff meeting. In the final weeks of the preseason, the Chiefs have seemed changeable at several positions, including linebacker and the right side of the offensive line.

“Getting close. But I don’t want to talk about specifics without our having the Friday afternoon staff meeting,” he said at the conclusion of Friday’s practice.

The Chiefs’ professed uncertainty at quarterback could be causing Baltimore’s defensive game-planners headaches. Cassel and Croyle are similar in style, but Thigpen demonstrated last year he’s more of a runner, more prone to breaking out and making things happen. But he’s also not as well suited to dropback passing as Cassel or the injury-plagued Croyle.

“I think this first (regular-season) game is difficult regardless of the circumstances,” Haley said. “When you add different variables in, how much you pay attention is probably up to each team individually. It’s a hard week regardless.”

One thing the Chiefs feel encouraged about is the improvement they’ve made on what last year was a historically bad pass rush. In four preseason games, they managed seven sacks, only three fewer than the NFL record they set last year in 16 games.

“We’ve been working on it a lot,” defensive end Glenn Dorsey said. “We’ve been putting a lot of emphasis on rushing the passer on third down — get him, and get off the field. It should be a lot better this year.”

Something else that’s different is the 3-4 defense the Chiefs have installed.

“We run a lot of different things, so it’s not just the 3-4,” Dorsey said. “When the opportunity comes on third down, they’re going to put us in the right situation to make the right plays. The sacks should come.

“What it comes down to is football. You’ve got to line up and beat the man in front of you. We’ve been working hard … I’m looking forward to it paying off.”