The dual-threat junior has helped turn the Cougars' season around. He's thrown for at least two touchdowns and run for at least 62 yards in the last four games, all BYU wins.
Nelson led BYU (6-2) to its best offensive game of the season last week, accounting for four touchdowns in the 59-3 rout of Idaho State. The Cougars rolled up a season-high 572 yards.
Nelson gives the improving Horned Frogs defense another stiff challenge going into their last nonconference game. Keeping him in the pocket is the key.
"We have to stay gap-assigned, even when we're pass rushing," Koontz said. "If you're containing, you have to keep contain. You can't let him out of the pocket."
While the Cougars are rolling on offense, TCU (5-2) is coming off its best defensive showing in the 69-0 dismantling of New Mexico. The Frogs responded to their bye week by holding the Lobos to just 85 yards -- the lowest for an opponent since 2008.
It was also the third time in the last four games that TCU allowed less than 300 yards. The Frogs' out-of-character struggles earlier this season were a manner of growing pains, Koontz said. TCU coach Gary Patterson has used 10 freshman and 12 new starters on defense so far.
"We knew we had an entirely different group of guys than we had last year," Koontz said. "We lost a lot of guys in the secondary. We're a younger defense. We lost [linebacker Tanner Brock] the first week. It's an evolving defense all year."
Patterson said the Cougars aren't doing anything new schematically on offensive, pointing out the Frogs have played BYU annually since moving to the Mountain West in 2005. But there is one distinction to these independant Cougars.
"The difference is the quarterback can run around and make plays," Patterson said.