Rachal is expected to play right guard against the Dallas Cowboys on Sunday, taking over for Tony Wragge, who started the first 10 games.

Rachal, a second-round draft pick, has shared time with Wragge over the past two games. He apparently made an impression on Singletary, who said Rachal "might have a chance to start. We'll see how it goes."

It would mark a long-awaited promotion for Rachal, who didn't take a single snap over the 49ers' first eight games. But Singletary has recently given increasingly favorable progress reports on the former USC standout, noting his work ethic in practice.

Rachal held back on celebrating Wednesday but acknowledged he is enjoying his increased playing time.

"Every game, I learn something different," he said. "I think I've done OK, but there are always things you can do better."

The offensive line has allowed just two sacks over the past two games, slowing the onslaught of the first half. Some of the improved showing has to do with new quarterback Shaun Hill, who gets rid of the ball quickly and excels in the short passing game.

Singletary also credited the linemen for coming together in offensive coordinator Mike Martz's system.

"You have a chance to build some continuity," he said. "You have a chance to figure out, 'I know how this guy plays and I have a comfort level with him. I'm feeling the quarterback.' It's just that time together really, really makes a difference."

Hill was selected as the NFC offensive player of the week. Against the St . Louis Rams , he became the first quarterback in 49ers history to compile a perfect passer rating of 158.3 in the first half. Overall, Hill completed 15 of 20 passes for 213 yards, two touchdowns and a passer rating of 142.3.

"It was kind of a surprise, but any time a quarterback gets an award like that, it's a direct reflection of how the whole offense played,'' Hill said. "In this case, it was about how the whole team played. The defense and the special teams set us up with field position."

Linebacker Patrick Willis made a surprise appearance on the 49ers' injury report with a hip strain. Willis was held out of practice as a precaution and will be fine to play against Dallas, a team official said.

Nobody on the injury report has been ruled out of the game. Others held out of practice were receiver Arnaz Battle (foot), safety Dashon Goldson (knee), receiver Josh Morgan (groin), cornerback Walt Harris (rest) and defensive end Justin Smith (rest).

Tight end Delanie Walker (shoulder) returned to practice on a limited basis after missing the Rams game. Tackle Barry Sims (ankle) participated at full strength.

The 49ers have yet to beat a team with a winning record this season. Their three victories are against teams with a combined 4-26 record. Still, the Cowboys aren't about to take the 49ers lightly.

"We lost to the Rams,'' Coach Wade Phillips said. "So we can't claim that we've beaten everybody with a winning record either."

Dallas is 0-2 against NFC West teams, losing 30-24 to Arizona and 34-14 to St. Louis.