Justin Roper, who led the Ducks to a win over South Florida in last season’s Sun Bowl, took over for Costa. He was knocked out with his own knee injury against Purdue in the third week.

Third-stringer Jeremiah Masoli displayed a strong but erratic arm last week in his first start. The junior college transfer, however, isn’t fully healthy after sustaining a concussion against Boise State.

And true freshman Chris Harper, who is more of a threat running the ball – he’s third on the team in rushing – tossed two interceptions in relief of Masoli against Boise State.

That’s why Ducks coach Mike Bellotti made the sudden decision to burn the redshirt year of true freshman Darron Thomas, who rallied the team late with three touchdown passes in a 37-32 loss to the Broncos.

So, who’s tossing the hot potato at quarterback for the Ducks this week against Washington State?

WSU coach Paul Wulff has no more insight than anybody else on what the Ducks will do for today’s Pacific-10 Conference clash at Martin Stadium in Pullman.

“We don’t have very much information about any (of the quarterbacks). The little bit on film is all we have,” Wulff said. “We just have to prepare for anybody, obviously.”

The thinking was that Thomas would start today, but early Thursday he and two teammates were involved in an automobile collision near Eugene that police are calling a street-racing incident. Thomas bruised the elbow on his throwing arm.

Masoli is feeling better, and has been cleared to play. Bellotti told reporters he would likely make his decision right before kickoff.

“I don’t know if it will change our game plan much, to be honest,” Wulff said. “I don’t think it really matters, probably because all three of their guys (Thomas, Masoli and Harper) are somewhat inexperienced as well.”

The Ducks’ passing game aside, Wulff has two other concerns about stopping an Oregon team that was one of the Pacific-10 Conference’s preseason favorites and is averaging 43 points per game. The Cougars have to figure out how to slow the Ducks’ running game – Oregon leads the conference, averaging 299.2 yards per game – and they’ll have to do it with a defense that has health issues.

Defensive tackle A’i Ahmu has been nursing a sore shoulder over the past couple of weeks and can’t take on a full load.

Matt Mullennix, a sixth-year player who has spent much of his career as a defensive end, will continue to see time at tackle, especially on obvious pass downs, Wulff said.

Linebacker-turned-defensive end Andy Mattingly, who led the Cougars in 2007 in tackles for loss (11) and sacks (eight), had his best showing in WSU’s 48-9 victory over Portland State last week. Wulff described Mattingly as “a little nicked up.”

“We’re hoping he has a good, healthy game and he’s a guy who can help us make some plays,” Wulff said. “We need Andy to play well.”

The Cougars also have their own quarterback issues. Last week, Gary Rogers (neck) and Kevin Lopina (back) suffered injuries, forcing Wulff to use redshirt freshman Marshall Lobbestael.

In what amounted to his first sustained college playing time, Lobbestael completed nine of 12 passes, threw for two touchdowns and 149 yards to earn Pac-10 offensive player of the week honors.

This will be Lobbestael’s first collegiate start, and Wulff said he’s as ready as he can be.

“He’s taking it very serious,” Wulff said. “When he’s out there, we seem to be fairly efficient.”

Extra points

Wulff said freshman quarterback J.T. Levenseller, the son of Cougars receivers coach Mike Levenseller, has been getting all the snaps with the second offense. … The Ducks have become more of a blitzing team in recent weeks, Wulff said, and he expects a lot of it considering Lobbestael’s inexperience. … Starting WSU cornerback Romeo Pellum is the nephew of Oregon linebackers coach Don Pellum.

Todd Milles: 253-597-8442

COUGARS GAMEDAY

OREGON (2-1, 1-0 Pac-10) AT WSU (1-3, 0-1)

Kickoff: 3:15 p.m., Martin Stadium, Pullman.

TV: FSN. Radio: 850-AM.

The series: The teams first met in 1901, and 85 games later Oregon leads the series, 40-38-7. WSU is 20-21-2 against Oregon in Pullman. The last time at Martin Stadium, WSU stunned them, 34-23.

What to watch: Both the Cougs and Ducks will be starting quarterbacks with about two quarters worth of college football experience. WSU’s Marshall Lobbestael had by most accounts a very good week of practice. Lobbestael isn’t one to get too flustered, but Oregon does have a capable pass rush and the Ducks will probably bring an assortment of blitzes and stunts to hurry and frustrate him. The Ducks haven’t officially announced their starter. Third-stringer Jeremiah Masoli suffered a concussion last week and he is doubtful. Freshman Darron Thomas had some solid moments last week in relief.

What’s at stake: It is still early, but Oregon needs to right itself quickly. The Cougs are getting Oregon at the right time with the Ducks’ QB issues so unsettled.

TNT pick: Oregon 31-24.

Prime numbers

Washington state

1Xavier Hicks, SS, 6-0/196, Jr.: His presence on the field made a big difference last week.

8Marshall Lobbestael, QB, 6-3/199, Fr.: Because of fire-red hair, he’s already earned the nickname Ocho Rojo.

52Greg Trent, MLB, 5-11/230, Sr.: He’s going to have to make tackles to stop Oregon’s vaunted ground game.

67Joe Eppele, OT, 6-8/294, Soph.: Struggled at times in his first start and must be better with the Ducks’ defensive ends.

80 Devin Frischknecht, TE, 6-3/251, Sr.: WSU’s offense is just harder to defend with him on the field as a receiving threat.

OREGON

1 Darron Thomas, QB, 6-3/200, Fr.: He was supposed to redshirt this season, but injuries forced him into starting.

9 LeGarrette Blount, RB, 6-2/240, Jr.: Leads the Ducks in rushing at 95.8 yards per game. Shares carries with Jeremiah Johnson.

15 Patrick Chung, DB/R, 6-0/210, Sr.: One of the hardest-hitting safeties in the country, he is also a dangerous return ma.

39 Will Tukaufu, DE, 6-4/272, Jr.: Nick Reed gets all the hype, but Tukuafu leads the team in tackles for loss (9.5) and sacks (5).

60 Max Unger, C, 6-5/300, Sr.: One of the Ducks’ best and most versatile linemen, he’s started games at left tackle and center.

Ryan Divish, The News Tribune