(AP) - Iowa is one of the nation's most surprising teams after answering nearly all of its preseason questions.
Now the No. 17 Hawkeyes have a new uncertainty to deal with: Can they keep winning while they keep losing guys?
Iowa (6-0, 2-0 Big Ten) is down five opening-day starters ahead of Saturday's West Division showdown at No. 20 Northwestern (5-1, 1-1).
The biggest blow came Tuesday, when coach Kirk Ferentz confirmed that star defensive end Drew Ott was lost for the season with a torn ACL in his right knee.
''It's a big void. But this team has done a good job of handling adversity,'' Ferentz said.
The Hawkeyes will have to do so again this weekend.
Ott, wide receiver Tevaun Smith (knee), running back LeShun Daniels (ankle), left tackle Boone Myers (neck stinger) and right tackle Ike Boettger (left ankle) were left off Monday's depth chart. Ferentz said it's doubtful any of them will play this week.
Even quarterback C.J. Beathard alluded to some extra soreness this week - he was seen with ice wrapped around his hip and groin after last week's 29-20 win over Illinois - but he said he'll play against the Wildcats.
''It's nothing serious,'' Beathard said.
Ott is Iowa's best pass rusher and arguably its best player. He is sixth in the Big Ten with 7 1/2 tackles for loss and five sacks despite being slowed by an elbow injury earlier this season.
Parker Hesse, a 240-pound freshman who played quarterback in high school and was a linebacker as a redshirt last season, will get the start in place of Ott.
''It's not on me or anyone else to fill everything that he brings. It's the entire defense. We're losing a lot,'' Hesse said.
The Hawkeyes' line struggled at times without their bookend tackles against Illinois. Iowa was forced to use a true freshman guard, James Daniels, at tackle. He'll likely be the first rookie to start there in Ferentz's 17 seasons this weekend.
But Iowa has had a much easier time replacing Tevaun Smith and LeShun Daniels.
That's because another Smith, freshman wideout Jerminic Smith, emerged as a potential star against the Illini - and Jordan Canzeri has shouldered the workload like no running back in school history.
Smith's first four career catches came against the Illini. He finished with 118 yards, highlighted by acrobatic grabs of 49 and 46 yards on third downs. Canzeri broke the school record with 43 carries for 256 yards, including 11 rushes in a row on Iowa's most crucial drive in the fourth quarter.
Daniels was supposed to be Iowa's workhorse back, with the smaller Canzeri as the change of pace guy. But Canzeri has proved to be the kind of lead back the Hawkeyes desperately need.
Still, Canzeri and the rest of the Hawkeyes could be forgiven for looking forward to next week, which will be Iowa's lone bye.
''When we get to the bye week it'll be nice to recover and rest a little bit. But right now we've just got Northwestern on our mind,'' Beathard said.
And the Wildcats will have bouncing back on their minds after losing 38-0 at then-No. 18 Michigan last week. Northwestern's unbeaten start, which began with a 16-6 win over then-No. 21 Stanford on Sept. 5, came to an end in ugly fashion.
''We just couldn't get out of our own way, offensively,'' coach Pat Fitzgerald said after his team allowed a 96-yard touchdown on the opening kickoff and trailed by four touchdowns by halftime. ''We'd put something together, we'd get a penalty, we'd get a drop, we'd get a missed assignment. So that's disappointing, obviously. It starts and ends with me.''
The Wildcats came in allowing a nation-best 7.0 points per game but allowed a season-high 21 in the first quarter. They weren't any better offensively, as Justin Jackson was held to a career-low 25 yards rushing on 12 carries for a Wildcats team that was averaging a Big Ten-best 248.8 yards on the ground. Northwestern managed 38 against the Wolverines.
"Not physical enough up front. ... Up front, we couldn't get any movement on our one-on-ones," Fitzgerald told the school's official website. "That made it tough sledding for Justin. We've got to get our run game going. That's our bread-and-butter. We've got to be able to run the football."
Northwestern will be without Matthew Harris for the foreseeable future after the cornerback suffered broken bones in his face on an apparent hit to the head by the knee of a running back last week.
Iowa has won the past two meetings, taking the latest 48-7 at home Nov. 1, 2014, despite Jackson rushing for 96 yards and a score.
The Wildcats have won the last two matchups at Ryan Field, the most recent in 2012.
"I think there's extra motivation because (Iowa is) in the driver's seat in the Big Ten West. That's the bottom line," Fitzgerald said.