Oklahoma has two regular-season games remaining against West Virginia and rival Oklahoma State, but Walker has been out of the lineup for more than a month due to a concussion. It's unclear whether Walker would have been available for either of those games, or the postseason. But Sooners defensive coordinator Mike Stoops left only one interpretation for how he viewed the decision.
Earlier this season, amid rumors of an early departure from the program, Walker addressed them with a social media post which read, in part, "I'll never leave my guys behind," per The Oklahoman.
NFL.com analyst Bucky Brooks doesn't believe Walker's draft value will be significantly damaged by his departure, but that doesn't mean Walker won't have to answer for the decision.
"Walker will have to answer to the severity of the concussion. He'll have to answer questions about why he left the team, because it does show a level of selfishness," Brooks said. "He'll also have to deal with the backlash, and whatever various things his coaches report to scouts. But at the end of the day, I don't think it will drastically affect his draft stock at all."
A pivotal factor for Walker will be whether or not the concussion was severe enough to sideline him for the balance of the season.
"If it's a situation where he could've come back, and willingly elected to step away from the team to help his stock, then you worry about the football character and what it means to him, and why does he play," Brooks said.
Underclassmen have until a Jan. 16 deadline to apply for early draft eligibility.
Walker (6-foot-2, 304 pounds) enjoyed a breakout season as a third-year sophomore in 2015, making 12 starts and recording 10 tackles for loss including six sacks from the defensive tackle position. This season, prior to his concussion, he had made seven tackles, two for losses, and four pass breakups in four games.
According to the Dallas Morning News, Walker also sustained a concussion prior to OU's Orange Bowl game against Clemson last year.