The Cougars survived losing two of their best players against TCU, but the numbers suggest replacing them for an entire game won't be easy.

BYU found a way to beat TCU without LJ Martin for nearly the entire game. The problem is that the offense didn't look much like the one that carried the Cougars through their first three wins. Now, with Martin and linebacker Isaiah Glasker both doubtful for Friday's matchup against Iowa State, No. 8 BYU faces a difficult test of its depth.

Head coach Kalani Sitake confirmed Monday that neither player is expected to be available after suffering injuries during BYU's 17-10 victory at TCU. "We're still evaluating yesterday and today, and we'll probably get more information, but right now it looks, you know, doubtful for both," Sitake said, according to the Deseret News.

The Cougars remain undefeated at 4-0, but Saturday's performance offered a pretty good look at what life without Martin could mean for the offense. BYU managed just 216 total yards, including 62 through the air, and needed two rushing touchdowns from quarterback Bear Bachmeier to escape Fort Worth with a win. The rainy conditions and TCU's strong defense certainly contributed, but the drop in offensive production was hard to ignore.

Replacing Martin is easier on paper than on the field

Martin entered the TCU game averaging more than 100 rushing yards per contest. Despite getting just two carries before leaving with an ankle injury, the reigning Big 12 Offensive Player of the Year still leads BYU with 344 rushing yards and three touchdowns on 44 attempts. His 7.8 yards per carry are a big reason the Cougars have been able to control games without asking Bachmeier to carry the offense himself.

BYU has some impressive numbers behind Martin. Journee Tonga has rushed for 157 yards on 19 carries, Devaughn Eka has 87 on 12, and Preston Rex has 94 on 18. Together, those three average 6.9 yards per carry, suggesting the Cougars have more than enough talent to keep running the football.

But there's a difference between producing in a supporting role and becoming the primary running back against a Big 12 defense. That difference showed up against TCU, when Tonga gained 28 yards on seven carries and Rex managed 21 on eight. Their combined 3.3 yards per carry was less than half their season average entering the week.

Bachmeier picked up much of the slack, rushing 15 times for 66 yards and both BYU touchdowns. Freshman Legend Glasker also contributed 26 yards on four carries, giving Aaron Roderick another way to get the ball outside. Still, relying on quarterback runs and receiver carries to replace Martin isn't necessarily a sustainable plan, especially with eight regular-season games remaining.

Tonga appears to have the highest upside as a traditional replacement, averaging 8.3 yards per carry through four games. Rex brings experience and versatility, while Eka has shown enough explosiveness in limited opportunities to deserve a larger role. BYU would be better served using all three rather than expecting one to suddenly become Martin.

The offensive line also needs to do more. BYU struggled with penalties and inconsistent blocking against TCU, putting additional pressure on inexperienced backs to create their own yards. Giving Tonga or Rex a clean lane on first down would do considerably more for the offense than simply increasing their carries.

Glasker's absence comes at a particularly bad time

Losing Isaiah Glasker might not generate the same attention as losing Martin, but his absence creates another problem against Iowa State. The senior linebacker has been one of BYU's most productive defenders over the past two seasons, recording five interceptions, 6.5 sacks and two forced fumbles across 2024 and 2025. He also brings experience to a defense that has held opponents to just 75 rushing yards and 14.3 points per game this season.

Kansas State transfer Jake Clifton is expected to take Glasker's place after filling in against TCU. Clifton recorded a sack in that game, while Nusi Taumoepeau added another as BYU finished with four sacks and held the Horned Frogs to 72 rushing yards. There is some encouraging news, too, with linebacker Siale Esera expected to return after missing two games.

Those performances suggest BYU has enough defensive talent to handle another injury. The bigger concern is the opponent.

Iowa State enters Friday averaging nearly 200 rushing yards per game, and running back Aiden Flora is coming off one of the best individual performances in the country. Flora rushed for 212 yards and three touchdowns against West Virginia while also throwing two touchdown passes in a 45-42 Cyclones victory. His performance earned him AP National Player of the Week honors.

Flora presents a much different challenge than the TCU running game BYU held in check last weekend. Iowa State has shown it can generate explosive plays on the ground, and missing an experienced linebacker makes defending those plays more difficult. Clifton and the rest of BYU's front seven will need to maintain their assignments, especially when Flora gets into the open field.

There is also a reason for optimism. While Iowa State piled up 577 total yards against West Virginia, its defense surrendered 518 yards and 42 points. BYU's offense should have opportunities to move the football, even without Martin, provided it avoids the mistakes that stalled so many drives against TCU.

Friday will tell us how good BYU's depth really is

The Cougars have already dealt with significant injuries this season, including losses along the offensive line and at running back. So far, the results haven't suffered. BYU is 4-0, ranked eighth nationally and sitting at 2-0 in Big 12 play.

But winning despite injuries doesn't mean those injuries aren't affecting the team. Against TCU, BYU needed a 59-yard interception return from Faletau Satuala to set up its first touchdown and a late Bachmeier rushing score to secure the victory. The defense was outstanding, but expecting it to carry that much of the load every week is asking a lot.

Friday's game should provide a better indication of whether BYU's replacements are ready for bigger responsibilities. Can Tonga and Rex produce against a starting defense for four quarters? Can Clifton help contain Flora? And can Bachmeier get the passing game going again without Martin drawing so much attention from opposing defenses?

With Notre Dame coming to Provo the following week, BYU has every reason to be cautious with injured players. But Iowa State is capable of making the Cougars pay for another slow offensive performance, regardless of its 3-2 record.

BYU survived the first test without Martin and Glasker. Friday will show whether the Cougars have enough depth to do more than just survive.

No. 8 BYU hosts Iowa State on Friday, October 9, at 8:15 p.m. Mountain Time on ESPN.