As Kelly Holcomb continued to prepare to start Sunday's game at Kansas City, coach Brad Childress remained coy about who will be his quarterback against the Chiefs.

Childress said Thursday that he was "still keeping it open" for Tarvaris Jackson to play. However, there is little to no chance of that happening. Jackson suffered a groin strain in the Vikings' 20-17 overtime loss to Detroit last Sunday and missed a second consecutive practice Thursday. Holcomb handled the bulk of the work with the first-team offense both days, virtually assuring him of starting.

The Wednesday and Thursday sessions are considered key, especially for a young quarterback, such as Jackson. "I'll be honest with you, Tarvaris needs every rep that he can get," offensive coordinator Darrell Bevell said. "He needs to be in there, he needs to be running the offense."

Holcomb getting the start will mean he has bypassed Brooks Bollinger on the depth chart. Bevell expressed no concern about Holcomb's ability to run the offense; the veteran was acquired in a trade from Philadelphia late last month.

"With the way that we do our installations it's like starting over every single week," Bevell said. "For the game plan we re-install every single play, so what is going to be in this game plan he is going to know. ... He'll have all of that down, and he'll have no problem."

Holcomb has not played in a regular-season game since 2005, when he started eight of the 10 contests in which he played for the Buffalo Bills.

Concern at safety

Strong safety Darren Sharper (hip) did limited work in Thursday's practice after sitting out Wednesday, but free safety Dwight Smith (hamstring) was unable to participate for a second consecutive day.

If Smith is unable to play Sunday, he likely would be replaced by veteran Tank Williams. Sharper was optimistic that he will be ready.

Mike Doss, another veteran safety, almost certainly will be active for the first time this season. He hasn't played since the second preseason game because of a calf injury but has been able to go full speed this week. Doss' last regular-season appearance came Oct. 22 when he suffered a knee injury playing for Indianapolis.

"I feel healthy," he said. "I can't wait to get back out there."

Etc.

• Running back Chester Taylor (hip), fullback Tony Richardson (forearm) and receiver Troy Williamson (hamstring) were limited in practice for a second consecutive day. For the Chiefs, tackle Damion McIntosh (knee) and safety Greg Wesley (knee) took part in all of practice, and safety Jon McGraw (hamstring) was taken off the injury report.

• The Vikings have the top-ranked kickoff coverage in the NFL with opponents' starting on average at their own 20.1-yard line.

• Nose tackle Pat Williams is slated to make the 100th start of his 11-year career on Sunday. He has not failed to start a game since the 2001 season when he missed the final three games with Buffalo because of a leg injury.

• Linebacker Napoleon Harris, who left the Vikings last offseason to sign with the Chiefs as a free agent, doesn't have any ill feelings toward his former employer. "I can't say [I left] on bad terms," Harris told the Kansas City Star. "I don't have any negative feelings toward the Vikings or their organization. They wanted me back, but we weren't on the same page." Harris has played well for the 0-2 Chiefs this season; he leads the team with 19 tackles and also has an interception.

Judd Zulgad • jzulgad@startribune.com