Here's our mistake. We routinely judge Illini football prospects by (1) the number of returning regulars and (2) the perceived quality of those starters.

We do it every year like clockwork.

But as Saturday's opener against Western Michigan gets under way, you'll notice a constant stream of interchangeable players. There'll be a mix of four Illini tight ends. You'll see a converted defensive back, freshman Justin Hardee, among the alternating receivers. Look for an offensive package featuring the versatile Miles Osei. Coach Tim Beckman is keeping an open mind at various positions.

"There'll be a set plan for substitution," Beckman said. "Each Thursday we meet with the players so they'll understand how the subbing will work. We have to keep the regulars fresh, and it's my belief that the only way young players will improve is in games."

One proviso: Whenever the opponent reaches the UI 25-yard line, the starters will be intact. The second-stringers will see their action in other parts of the field.

It is this universal reliance on depth that sets apart the top teams from the also-rans. Injuries happen. So does fatigue. And sub-par performance. That's why the premier teams, those with quality reserves, improve month by month, and the mediocre teams tend to stagnate.

Beckman repeatedly has mentioned depth as his main concern.

"We've got to keep fresh bodies out there because Western Michigan moves at such a fast pace," he said. "This is a question that must be answered. Can we count on our twos and threes?"

Playing the percentages

There was a time — three decades ago — when the UI's defensive coordinator, Max McCartney, assigned percentages at each position, 50-50 or 70-30 or whatever. After a set number of plays, a defender automatically came out. This served the double purpose of keeping regulars fresh for the fourth quarter and developing younger reserves for the future.

As first-year coordinator on defense, Tim Banks said, "Everybody is going to play Saturday, and we'll adjust as we go. It is time to execute with the lights on. We have some unknowns."

Two raw freshmen, Mike Svetina and Mason Monheim, are listed behind Jonathan Brown and Houston Bates at linebacker. Another freshman, Ta'Jarvis Fuller, has a cast on his hand as he backs up senior rover Ashante Williams.

Earlier, when key backup Henry Dickinson fractured his leg, linebackers coach Mike Ward planned to alternate sophomore Ralph Cooper for Brown and Bates. But Cooper is serving a first-quarter suspension Saturday.

"The first guys in will be young," Ward said. "You can't play 11 guys the whole game. We'll stick with our rotation, but it will be based on the series and the number of plays. On third down and in the red zone, we want to get the regulars in."

With Brown an outstanding blitzer, Ward will keep the Broncos guessing as to his position.

"These spread offenses tend to attack the boundary with their skill receivers," Ward said. "Jonathan can make a lot of plays, and blitzing is what he does best. If I told where he'll be coming from, it wouldn't be a secret."

Pass happy

While unpredictable weather may dictate Saturday's strategies, the game probably will turn on the UI's ability to control Western Michigan's aerial game. It remains a truism that no one can prevent the perfectly executed pass.

Coach Bill Cubit is an aerial expert in a pass-minded Mid-American Conference. He sees the Broncos' controlled passing game as the best avenue to overcome Illinois superiority in its defensive front seven. He arrived at Western Michigan a year after Illinois defeated the Broncos 30-27 in 2004 and personally stands 1-1 in the series.

When quarterback Alex Carder was sidelined last November against Akron, the backup (Trevor Van Tubbergen) threw six TD strikes. The Broncos' stats in their last five games were astounding: 2,218 yards passing, 152 first downs and an average of 46.2 points. This includes Carder's 439-yard aerial effort against Purdue in Detroit on Dec. 27, the Boilermakers prevailing 37-32 by recovering two critical onside kicks and intercepting four Carder passes.

Graduation took a receiving corps that included the nation's pass-catching leader, Jordan White, but Carder returns behind an experienced line featuring two transfers from Michigan and Michigan State. Defensively, a speedy 3-3-5 defensive alignment allows for creativity to confuse UI plays.

The Broncos return to Memorial Stadium with the belief that they let last year's 23-20 loss slip from their grasp. They see a grand opportunity in the MAC West because last year's co-champs, Northern Illinois and Toledo, must come to Kalamazoo.

Loren Tate writes for The News-Gazette. He can be reached at ltate@news-gazette.com.