Neither Obomanu nor Williams practiced this week. Obomanu suffered a severe laceration on his right hand, while Williams was rolled up on and sprained his left ankle last week against Carolina.
Carroll says he is expecting Obomanu to play. Obomanu is being fitted with special protection for his hand.
"He's got stitches in his hand [and] they're going to be there on game day," Carroll said. "We just got to see how it works for him and see how the little device they've been putting on his hand works out for him and all that."
Williams, Seattle's leading receiver, is more of a question. Williams played last week after missing a game with a foot strain. Carroll says Williams did more running in preparation for last week's game than he has this week.
"Mike's a little more of an issue because we've got to make sure he can run full-speed on Sunday," Carroll said.
The Seahawks should get a boost on the defensive line with the return of defensive tackle Colin Cole from a serious high-ankle sprain.
Cole was hurt on Oct. 31 against Oakland, late in the fourth quarter when Cole says a Raiders offensive lineman "jumped" on the side of his lower leg.
"As far as something to work back [from] and knowing I'm coming back, this is the longest, and the toughest, knowing that I had the opportunity to come back," Cole said. "It was definitely the toughest thing having to sit back and watch the guys play."
Seattle also lost defensive end Red Bryant in the game against the Raiders to a season-ending knee injury.
The shuffling of bodies needed to fill those two major gaps has led to the Seahawks' run defense taking a beating.
In the five games since Cole and Bryant went down, the Seahawks are allowing an average of 130.2 yards rushing. At its high point early in the season, Seattle ranked second in the NFL at stopping the run. With four weeks left in the regular season, they are 21st.
"It seems like it's been an extremely long time. I've missed getting out there with the guys and it's been pretty hard watching the games and watching your teammates and especially knowing that I couldn't help them as I would have liked to have," Cole said. "Hopefully I can help come back and contribute."
His return also allows a bit of flexibility to return to Seattle's defensive line. While he was out, Junior Siavii filled in and played well, but the lack of depth became an issue. With Cole back, Seattle can rotate Siavii at defensive tackle but also use his bigger body at defensive end to help against the run.
"We're going to see on Sunday just like everybody else," Seattle defensive end Kentwan Balmer said. "Colin is a great player, Junior is a great player, we have a lot of good players on this defensive line. We'll see what happens."
Carroll also said offensive lineman Chester Pitts will likely be out against the 49ers.
Information from The Associated Press was used in this report.