The Boise State football team enters the stretch run of the Mountain West season with a depleted secondary for the second straight year.

The No. 19 Broncos have lost third cornerback Bryan Douglas for the rest of the season with a torn anterior cruciate ligament and suspended starting safety Lee Hightower indefinitely for an unspecified team-rules violation.

The depth is shaky enough that coach Chris Petersen is considering taking a true freshman off the redshirt track and inserting him into the defensive backfield with just four regular-season games left.

He did not identify candidates.

Boise State (7-1, 4-0 Mountain West) hosts San Diego State (6-3, 4-1) at 8:30 p.m. Saturday.

“We’re not going to waste anybody’s year,” Petersen said. “If we’re going, we’re going, and that guy’s going to get good quality reps and it’s going to springboard him into next year.”

Douglas started the first three games and played regularly in situations where the Broncos used three cornerbacks and two safeties. He’s tied for 15th on the team with 19 tackles.

Hightower, a sophomore, started every game until he was suspended for last week’s game at Wyoming. No. 3 tight end Hayden Plinke, a true freshman, also was suspended for that game.

Neither player is practicing with the team and there is no timetable for their return, Petersen said.

Hightower is eighth on the team with 31 tackles and was having an outstanding season. Redshirt freshman Darian Thompson, who has rotated into games all season, replaced him last week and will start Saturday.

“Darian’s done great all season,” Petersen said. “We’ve kind of thought of him as a starter as well. He didn’t disappoint.”

Redshirt freshman Dillon Lukehart moves into the backup spot behind Thompson. Sophomore transfer Deon’tae Florence and junior Ebo Makinde are the backup cornerbacks.

Last year, Boise State lost three of its top four cornerbacks to injuries. The Broncos allowed 473 passing yards in a loss to TCU and 350 in a win against San Diego State during the height of the injury problems.

OTHER INJURIES

In addition to Douglas, defensive end Kharyee Marshall, nickel Dextrell Simmons and defensive tackle Greg Grimes left the Wyoming game with injuries. Petersen said they all fall into the day-to-day or week-to-week categories. He does not provide details on short-term injuries.

MW TITLE RACE

Boise State is the only Mountain West team without a conference loss. Fresno State, San Diego State and Air Force are each 4-1.

If Boise State wins this week, the Broncos need only to beat Hawaii (1-6) and Colorado State (2-6) to clinch at least a share of the title.

If San Diego State wins, the race gets murky. Fresno State and San Diego State still must play Air Force. Boise State does not play the Falcons this season.

The Broncos finished second behind TCU last year.

“That’s something we talked about all offseason,” quarterback Joe Southwick said. “We didn’t get the job done last year and we have an opportunity this year to get it done, so we’re all in, we’re going to work as hard as we can and be as prepared as we can.”

WINNING AGAIN

Boise State has clinched its 15th straight winning season — a streak that started in 1998.

The Broncos have won at least nine games for 10 straight seasons, at least 10 for six straight and at least 12 for four straight.

PLAYERS OF THE WEEK

Boise State’s internal players of the week were tailback D.J. Harper (offense), linebacker J.C. Percy (defense), nickel Corey Bell (special teams) and center Matt Paradis (lineman).

Chadd Cripe: 377-6398, Twitter: @IDS_BroncoBeat