Walker left the game after carrying three times for 36 yards, including a 30-yard run that set up a touchdown on their first possession. Walker's right ankle was examined extensively on the sideline before he was ruled out early in the third quarter.
"I can't tell you because it's not an ankle sprain," coach Pete Carroll said after the game. "He jammed it, so I'm not quite sure of what to tell you right now. We don't know."
Walker, Seattle's second-round pick, took over as the Seahawks' starter after Rashaad Penny suffered a season-ending ankle injury in October. He entered Sunday with 613 rushing yards and nine touchdowns to rank second and first, respectively, among rookies.
The Seahawks were already missing one running back Sunday with Travis Homer (illness/knee) inactive.
DeeJay Dallas injured his ankle late in the first half and limped into the locker room but stayed in the game to lead Seattle with 37 rushing yards on 10 carries. Tony Jones Jr., who hadn't played an offensive snap since the Seahawks claimed him off waivers from the New Orleans Saints in October, added 14 yards on seven carries.
"I was really praising DeeJay Dallas for fighting through being banged up and finishing for us," Carroll said. "Tony did a nice job coming in for us and unfortunately Ken, he jammed his ankle and he just couldn't get back out there and get going again. He showed that he was ready to go and all, but he just couldn't get back out, so we'll have to see what that means."
With Walker out and Dallas playing at less than 100%, the Seahawks leaned on Geno Smith at the end. He capped a 10-play, 70-yard drive with an 8-yard touchdown pass to DK Metcalf. Smith went 6-of-9 for 65 yards on that drive, with Seattle running the ball only once. According to ESPN Stats & Information research, it was the first go-ahead touchdown pass of Smith's career in the final minute of regulation or overtime.
"It's what these guys do when they're great and he did one today," Carroll said. "It's an all-time comeback drive and he did it perfectly."
Smith finished with a career-high 367 yards on 28-of-39 passing. His interception came on a play in which former Seahawk Bobby Wagner ripped the ball out of Jones Jr.'s hands after he had fallen to the ground but before he had completed the catch.
A stuffed-up sounding Smith confirmed that he was playing sick. He caught the illness that went around the Seahawks' facility this week, sidelining eight players in Thursday's practice.
"I've been struggling, man," Smith said. "I woke up today hurting and just kept fighting, kept going, kept going, kept going and God is good."
Safety Ryan Neal, who was questionable entering the game with elbow and shoulder injuries, missed the fourth quarter after hitting his knee on the turf.
"He did a bursa [sac], meaning that he's got some swelling in the front of his knee," Carroll said. "It hit the ground. So it's not a knee injury as much as he got smacked and it ballooned up on him a little. So we'll see what happens."