BOISE - For the second straight year, Boise State has to adjust to the loss of key players in the secondary of its highly ranked defense.

But this year, the No. 19 Broncos (7-1, 4-0 Mountain West) are confident they have enough senior leaders and seasoned underclassmen to avoid the kind of meltdown that contributed to a late-season loss to TCU last year that spoiled an undefeated season and any lofty postseason plans.

Coach Chris Petersen said Bryan Douglas, who started the first three games and the No. 3 cornerback, will miss the rest of the season after tearing an ACL in last week's 45-14 rout at Wyoming. Petersen also said starting safety Lee Hightower's suspension for violating team rules will remain in place at least through Saturday's matchup with San Diego State (6-3, 4-1).

Hightower, who has 31 tackles and one interception, was disciplined last week and didn't travel with the team to Wyoming. Petersen declined to share any details of the decision and was clearly irritated when quizzed about the status of the redshirt sophomore Monday.

"I haven't talked to Lee," said Petersen, offering no timetable for Hightower's return. "He is not back this week."

Petersen also said Dextrell Simmons, who plays a hybrid linebacker/defensive back position, is day-to-day after leaving the Wyoming game early with an undisclosed injury.

For now, Hightower will be replaced by redshirt freshman Darian Thompson, who has played in all eight games, mostly in nickel and dime packages. Thompson has 24 tackles, two interceptions and the confidence of coaches to step into a starting role.

"At this part of the season, I think everybody's role increases," said Petersen. "If you don't have enough guys with four games left in the season, that's how it goes."

With the win in Laramie, Wyo., Boise State won its seventh straight and sits alone atop the conference standings, one game ahead of Fresno State, San Diego State and Air Force. The Broncos also edged up to No. 19 in the BCS Standings, and if they can go undefeated the rest of the way, elbow into the top 16 and beat out a champion from one of the automatic qualifying conferences, they would earn an invitation bid to one of the prestigious postseason bowls.

But the setbacks in the secondary at this point in the season are eerily reminiscent of last year when the Broncos suffered a rash of injuries to key players that left the backfield reliant on Hightower and other young, inexperienced defenders down the stretch.

Starting cornerbacks Jamar Taylor and Jerrell Gavins, along with backup cornerback Ebo Makinde, were rehabbing from season-ending injuries when the Broncos - undefeated and ranked No. 5 at the time - met the Horned Frogs on Nov. 12 with the conference title on the line.

TCU and quarterback Casey Pachall wasted little time exploiting the Boise State's youth. Pachall threw for 473 yards and five touchdowns, including scores of 75, 74 and 69 yards in the first half. The Broncos rallied in the second half, but the comeback fell short when kicker Dan Goodale's last-second field goal sailed wide of the uprights, ending Boise State's BCS and conference title dreams.

The good news is the Broncos still have three of its four starters in the secondary. Taylor and Gavins are healthy and anchoring a pass defense that has forced 23 turnovers and ranks in the top ten nationally in scoring, passing yards allowed and passing efficiency defense.

Taylor ranks second on the team with 40 tackles and has two interceptions, while Gavins has one pick and a fumble return for a TD. The duo is also a big reason the Broncos are allowing an average of 165 yards per game through the air.

Taylor says he and Gavins are ready to assume a leadership role with their younger teammates, whether it's extra communication before the snap to spending more time with them during film study.

"I think it just makes us better, to get the young guys in there to learn a little more," Taylor said. "Obviously we want our guys, but we've got to have guys to carry the flag and keep the ball rolling."

Still, Petersen and his staff are considering filling the void created by Douglas' injury with a freshman pegged to take a redshirt this season. In the past, Petersen has resisted the urge to pull a redshirt late season, but acknowledged the need to add some depth in the backfield.

''We'll keep our fingers crossed that we stay relatively healthy from here on out," Petersen said.